Refrigeration system and method of operating the same

ABSTRACT

A refrigeration system including a compressor, condenser, valve, and refrigeration branch, all of which is in fluid communication. The refrigeration branch includes an evaporator coil. The refrigeration system further includes a case adapted to be cooled by the evaporator coil, and a system controller operable to control one or more aspects of the refrigeration system, and a subsystem controller in communication with the system controller. The subsystem controller is operable to control a subsystem having one of the compressor, condenser, valve, refrigeration branch, and case. The method of operating the refrigeration system includes at the subsystem controller, monitoring a parameter of the subsystem, comparing the monitored parameter with a parameter limit, generating an alarm when the parameter is not within the parameter limit, and communicating the alarm to the system controller.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/461,123, filed Jun. 12, 2003 now U.S. Pat. No. 6,973,794, entitled“REFRIGERATION SYSTEM AND METHOD OF OPERATING THE SAME”; which iscontinuation-in-part of U.S. patent application Ser. No. 09/849,900,filed on May 4, 2001, entitled “DISTRIBUTED INTELLIGENCE CONTROL FORCOMMERCIAL REFRIGERATION,” issued as U.S. Pat. No. 6,647,735; which is acontinuation-in-part of International Patent Application No.PCT/US01/08072, filed Mar. 14, 2001, entitled “DISTRIBUTED INTELLIGENCECONTROL FOR COMMERCIAL REFRIGERATION”; which is a continuation-in-partof U.S. patent application Ser. No. 09/524,939, filed on Mar. 14, 2000,entitled “DISTRIBUTED INTELLIGENCE CONTROL FOR COMMERCIALREFRIGERATION,” issued as U.S. Pat. No. 6,332,327; all of which areincorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to a refrigeration system and, more particularly,a refrigeration system including a system controller and one or moredevices having respective control modules, where the refrigerationsystem is adapted to be reconfigured, at least in part, automaticallywhen an alarm is generated in one of the control modules.

BACKGROUND

Intelligent electronic control for refrigeration systems (e.g., acommercial refrigeration system such as can be found at a supermarket)requires extensive configuration of the operating and safety parametersof the system. The configurable parameters are specific to thesubsystems and devices to which the controls are attached and varyaccording to the application. In order to properly protect bothequipment and refrigerated product, electronic controls applied tocommercial refrigeration systems employ an alarm condition action andnotification strategy. These alarm conditions can be categorized ascontrol and safety. Control alarm conditions exist when a monitored orcontrol parameter exists outside predetermined operational limits.Safety alarm conditions result when a monitored or calculated parametertraverses a predetermined safety limit.

Existing electronic controls for commercial refrigeration systemsrequire installing personnel to determine all alarm limits and aremanually configured in the system controller. Subsequent to installationand start-up of the refrigeration system, operating and servicepersonnel can modify these limits. Each of these scenarios providesopportunity for the implementation of erroneous operational and/orsafety alarm limits. These errors will go unnoticed until they result inproduct loss, catastrophic equipment failure, or property damage.

SUMMARY

Alarm conditions can be categorized as control and safety. Controllimits form the boundaries that define the desired or normal range ofoperation. When a measured or calculated process parameter violatesthese boundaries, corrective action is taken by the control. This actioncan include alteration of system operation and/or notification ofservice personnel. Dependent upon the nature of the alarm, the controlsystem can delay action for a predetermined period to allow the systemto stabilize. This is done to avoid “nuisance” alarms or those caused bytransient environmental conditions. Safety limits are defined as thosethat, when exceeded or satisfied, are indicative of imminent equipmentfailure. Action taken by the control system is immediate and decisive.Operation of the offending equipment or device is discontinued andservice personnel are notified.

In one configuration of a refrigeration system embodying the invention,implementation of a distributed control methodology places intelligenceat the point of control and/or sensing. Division of the control tasksand distribution of the control/monitoring devices segregates systemoperating parameters. To regain system wide control and monitoringcapability, a communication network (or series of networks) isestablished among subsystems and monitoring devices. The network(s)provide(s) an infrastructure for the sharing of operating parametersamong the control and/or monitoring devices and a system wide mastercontrol.

Application of distributed control to a commercial refrigeration systemplaces control and monitoring processes in individual device modules (ordevice controllers). Distribution of the control intelligence inherentlydisperses the alarm generation and required action activity across theattached modules. The stored limit values, as well as required actionactivity, are specific to the parameters sensed and/or operated on bythe modules. The alarm limit values are stored locally in each of theattached modules and may be mirrored at the system controller.

An automatic configuration method can be utilized to identify orgenerate alarm limit values. If automatic configuration is used,applicable alarm limit values are retrieved, once identified, fromprogrammed look-up tables or calculated using specific equipment data inconjunction with operating and application data. The appropriate alarmlimit values are transmitted to the modules. The values are then usedduring operation by the modules and the system controller for comparisonwith sensor data to determine the existence of alarm conditions. Buythis process the need for human intervention to establish and modifyoperational and safety alarm limit values is reduced or even eliminated.

The alarm condition determination, action, and notification process usedin some constructions of the invention differs from that employed bycentral control systems. Safety limit exceptions are sensed and actedupon by the attached module. The module terminates operation of theattached equipment. In some constructions, the termination of theoperation as well as the offending safety parameter is then reported tothe system controller. The system controller then determines theappropriate notification and alarm response to store and servicepersonnel.

In one construction of the refrigeration system, the system controller,under normal operation, determines system operational alarm conditionsand appropriate course of action. The system controller has access toall sensed data from each of the attached modules and knowledge of thecurrent state of all attached equipment. This advanced level of systemoperational information allows for more intelligent operational alarmcondition determination and intelligent system control reaction. Inanother construction, in the event of a system controller or networkfailure, the modules operate autonomously. The operational alarmdetermination, response, and notification take place in the module underthese circumstances.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a refrigeration system.

FIG. 1A is an schematic flow diagram of a second refrigeration systemsuitable for use in connection with a distributed intelligence controlsystem.

FIG. 2 is a schematic representation of one construction of a buscompatible compressor safety and control module.

FIG. 3 is a schematic representation of a compressor.

FIG. 4 is a flow diagram illustrating an exemplary operation of thecontrol and safety module in a standard operating mode.

FIG. 5 is a flow diagram illustrating an exemplary operation of thecontrol and safety module in a master controller failure mode.

FIG. 6 is a schematic representation of aspects of a solid state relaydevice.

FIG. 7 is a system block diagram illustrative of aspects of a commercialrefrigeration system.

FIG. 8 is a block diagram illustrating aspects of a partially wirelessconfiguration of the commercial refrigeration system of FIG. 7.

FIG. 9 is a block diagram of a bus compatible branch control subsystem,suitable for use with the commercial refrigeration system of FIGS. 7 and8.

FIG. 10 is a block diagram of a commercial refrigeration systemincluding bus compatible valve control.

FIG. 10A is a block diagram of an exemplary construction of the systemof FIG. 10 using valve controller to control an evaporator valveassociated with a subcooler.

FIG. 11 is a block diagram that illustrates a system using modular casecontrol modules to provide monitoring and control functions for aplurality of refrigeration display cases.

FIG. 12 is a block diagram that illustrates the use of a modular casecontroller configured for display case monitoring.

FIG. 13 is a block diagram that illustrates the use of a modular casecontroller to provide branch control for a plurality of display casesconfigured in a refrigeration branch.

FIG. 14 is a block diagram illustrating the reduced wiring requirementsassociated with using a distributed intelligence refrigeration controlsystem.

FIG. 15 is a schematic representation of a second construction of a buscompatible compressor safety and control module.

FIGS. 16A–16F are flowcharts representing one method of dynamicallycontrolling a plurality of multiplexed compressors.

FIG. 17 is a table representing parameters identified as rackparameters, which are communicated to and from the rack PLC in FIG. 7.

FIG. 18 is a table representing parameters identified as suction groupparameters, which are communicated to and from the rack PLC in FIG. 7.

FIG. 19 is a table representing parameters identified as system dataparameters, which are communicated to and from the rack PLC in FIG. 7.

FIG. 20 is a table representing parameters identified as suction groupparameters, which are communicated to and from the rack PLC in FIG. 7.

FIG. 21 is a table representing parameters identified as condenserparameters, which are communicated to and from the rack PLC in FIG. 7.

FIGS. 22A, 22B, 22C, and 22D are schematic representations of a 256-bitmemory coupled to the microprocessor 1505 in FIG. 15.

FIG. 23 is a flowchart of a read sequence for one method ofcommunication between the master controller 70 and the BCCSCM 1500.

FIG. 24 is a flowchart of a write sequence for one method ofcommunication between the master controller 70 and the BCCSCM 1500.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways. Also, it is to be understood thatthe phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” or “having” and variations thereof herein ismeant to encompass the items listed thereafter and equivalents thereofas well as additional items. Unless specified or limited otherwise, theterms “mounted,” “connected,” “coupled” and “communication” andvariations thereof herein are used broadly and encompass both direct andindirect mountings, connections, couplings and communications. Further,“connected,” “coupled,” and “communication” are not restricted tophysical or mechanical connections, couplings, or communications.

Referring now to FIG. 1, one construction of a refrigeration system(e.g., a commercial refrigeration system for use in a food store) isshown to comprise one or more fixtures (which are illustrated as fooddisplay merchandisers 10A and 10B in the shopping arena of a foodstore). The merchandisers 10A and 10B each incorporate at least oneevaporator coil 12A and 12B (or like heat exchanger unit), respectively,disposed for cooling the merchandiser. Three multiplexed compressors(designated 14A, 14B, and 14C, respectively) are connected by way of asuction header 16 and a low side return pipe 18 in fluid communicationwith the low side of the evaporators 12A and 12B for drawing refrigerantaway from the evaporators. A condenser (generally indicated at 20)including a fan 22 and heat exchanger 24 is in fluid communication onthe high discharge side of the compressors 14A, 14B, 14C for removingheat and condensing refrigerant pressurized by the compressors. Althoughan air-cooled condenser 20 is shown, other types of condensers, such asthose liquid cooled from a ground source water supply, may be used.Moreover, it is to be understood that the single illustrated fan 22represents one or more fans typically used in a condenser for commercialrefrigeration applications.

Refrigerant from the condenser 20 is stored in a receiver 26 incommunication with expansion valves 28A and 28B by way of a high sideliquid delivery line 30. The expansion valves 28A and 28B meterrefrigerant into respective evaporators 12A and 12B and induce apressure drop for absorbing heat, to complete the refrigeration circuit.The compressors 14A, 14B, and 14C, and usually also the suction header16 and receiver 26, are mounted on a compressor (or condensing unit)rack (not shown) prior to shipment to the store location where therefrigeration system is to be installed.

The food display merchandisers 10A and 10B illustrated with theevaporators 12A and 12B can be placed in the shopping arena of a foodstore. However, it is understood that other types of cooling fixturescould be placed in other parts of the store (e.g., a service area orbackroom cooler). The liquid line 30 and suction return line 18 havebeen broken to indicate connection to other evaporators (not shown) inthe system. Evaporators may be connected to the same piping circuitbetween the receiver 26 and the suction header 16, or in a differentcircuit or “branch” (not shown) connected to the receiver. Further, thenumber of compressors 14 in the refrigeration system can be more or lessthan three (including only a single compressor). The refrigerationsystem typically includes a compressor, a condenser, an expansion valveand an evaporator. Other components can be included but are notessential, and the precise mounting or location of the system componentsmay be other than described. Moreover, the same aspects of therefrigeration system have application outside the food storeenvironment; for example, the invention can be used with cooling otherperishable, non-food products such as blood, plasma and medicalsupplies. Also, some aspects of the communications network (discussedbelow) have application in other systems.

As shown in FIG. 3 and in one construction, each compressor 14A, 14B,and 14C comprises an electric motor 32 driving a shaft 34 connected to apressurizing unit 36. For purposes of the description herein, compressor14A will be referred to; the other compressors 14B and 14C preferablyhaving the same construction. The pressurizing unit may take on anysuitable form. In one construction, reciprocating pistons driven by amotor constitute the pressurizing device, but more and more, the quieterrotary devices found in scroll compressors and screw compressors arebeing employed to compress the vaporous refrigerant. A scroll compressoris illustrated in FIG. 3. The compressor 14A has a low side suctioninlet 38 that receives the vaporous refrigerant from the evaporators 12Aand 12B and a high side discharge outlet 40 through which hot,pressurized refrigerant is discharged from the compressor. In oneconstruction, the motor 32 and pressurizing unit 36 aresemi-hermetically or hermetically sealed within an outer casing or shell42. The motors 32 of the compressors are each connected to a respectivehigh voltage (e.g., three phase 480 V AC or 208 V AC) power line 44A,44B, and 44C (FIG. 1) extending from a power distribution center 46within the food store. These lines are shielded, such as by placementwithin a conduit, as may be required by electrical codes.

In one construction, the compressors 14A, 14B, and 14C each have a buscompatible compressor safety and control module 48 (also referred to as“BCCSCM,” “compressor operating unit, “compressor control module,” or“compressor controller”) for monitoring at least one, but preferablyseveral operating conditions or parameters of the compressor. The“operating parameters,” in one construction, include (1) controlparameters providing information used for controlling the compressor 14,and (2) safety parameters providing information about whether thecompressor 14 is operating within its designed operational envelope orin a manner which could damage the compressor 14. It is envisioned thatany number of parameters could be monitored, including only safetyparameters or, less likely, only control parameters. Control parametersfor the compressor 14 may include, but not limited to, suctiontemperature, suction pressure, and discharge pressure. Safety parametersfor the compressor 14 can include, but not limited to, dischargepressure, discharge temperature, oil level (or pressure), phaseloss/reversal, and motor winding temperature. As is apparent, some ofthe control parameters are also classified as safety parameters.

The bus compatible compressor safety and control module (“BCCSCM”) 48 isconstructed and arranged to receive and/or detect the various operatingparameters and control operation of the compressor. In one construction,the BCCSCM comprises a processor 49 and multiple sensors incommunication with the processor 49. In the illustrated construction ofFIG. 3, the compressor 14A is built with individual continuous readinganalog sensors including a discharge pressure sensor 50, a dischargetemperature sensor 52, a suction pressure sensor 54, a suctiontemperature sensor 56, and a motor winding temperature sensor 58 (FIG.3). In one construction, the temperature sensors 52, 56 and 58 arevariable resistance, RTD-type sensors. An oil level sensor 60 can be ofthe type that changes the state of a circuit when the oil level fallsbelow a predetermined minimum, and does not provide a continuous readingof the oil level. A power phase monitoring device 62 incorporated intothe BCCSCM 48 is capable of detecting both phase loss and phase reversalon the three phase power line 44A coming into the compressor 14A. It isto be understood that other sensors can be used (e.g., digital sensorsas discussed below).

In one construction of the commercial refrigeration system, the sensors50–62 are installed at the compressor assembly site and disposed withinthe hermetically (or semi-hermetically) sealed shell 42 of thecompressor (FIG. 3). This construction allows the sensors 50–62 to beprotected in the shell 42 and, particularly in the case of the suctionpressure sensor 54, are located close to the pressurizing unit 36 formore accurate readings of compressor function. However, it is to beunderstood that the sensors 50–62 could be located other than in theshell 42. For instance, it is envisioned that sensors could bereplaceably received in openings 59 in the shell (schematicallyillustrated in phantom in FIG. 3) accessible from the exterior, orexternal to the compressor shell as in the case of a reciprocatingsemi-hermetic compressor, or any other motor driven compression device.

The processor 49 of the BCCSCM 48, in one construction, is a dualprocessor system, including a host controller (such as amicrocontroller, an ASIC, or a microprocessor, any of which may beconnected to a memory) and a communication slave controller. The hostcontroller and communication slave are not separately represented inFIG. 2, but are collectively represented as the processor 49. In oneconstruction, the host controller has a 256 byte internal RAM, 8kilobytes of flash program memory, and 16 input/output pins for controlinterface. The communication slave, in one construction, is anapplication specific integrated circuit (ASIC) that communicates withthe field bus network (described in one construction below asAS-Interface® network). The communication slave translates the protocolof the field network into a signal understood by the host controller,and vice versa.

For an exemplary construction of the communication slave, if the fieldbus network provides four data bits per message, the communication slavecan be configured to extend the data capabilities of the field busnetwork by interfacing with an intermediate memory device (an additionalRAM) between the communication slave and the host controller. In such aconstruction, the communication slave and the host controller interfacewith the RAM to extend the data capabilities of the field bus network byusing sequential read or write cycles of the field bus network to buildlarger data sizes. In other words, rather than limiting the data sizesto four bits, larger data sizes are constructed by grouping multiplefour-bit data transmissions. The communication slave sequentially writesthe data into (or reads the data from) the additional RAM. The hostmicrocontroller reads the data from or writes the data to the additionalRAM. Thus, for example, a sixteen-bit data parameter may be constructedover the course four successive data cycles.

Alternative structures of the BCCSCM can also be employed. For exampleand as shown in FIG. 15, the BCCSCM 1500 includes a microprocessor 1505,RAM 1510, and program memory 1515. The BCCSCM 1500 also includes acommunication slave 1520, a suction sensor 1525, a discharge sensor1520, an oil sensor 1535, a current sensor 1540, and a voltage sensor1545. The BCCSCM 1500 also further communicates with the compressor 14to receive switched contact input from a high-pressure cut out 1550 andoil level sensor 1555 and communicates with a compressor on/off control1560.

In other constructions of the refrigeration system, a field bus protocolhaving larger inherent data sizes could be accommodated, therebypotentially eliminating the need for a communication slave to translatethe protocol. In yet another construction, the communication slave andthe host controller (or microprocessor 1505) are combined as singlecontroller (e.g., a single ASIC) or as a single microprocessor andmemory. Unless specified otherwise, when referring to the constructionshown in FIG. 2, the description also applies to the construction shownin FIG. 15.

The host controller (e.g., microprocessor 1505) is adapted to receivesignals from the sensors indicative of the values of the sensedoperating parameters. The host controller also stores safety limitvalues for the measured safety parameters, respectively. The hostcontroller is capable of generating digital status informationindicative of the values of the operating parameters. When a safetylimit is traversed, the host controller is capable of generating adigital status information signal including specific information as towhich safety parameter is out of specification. The signals aretranslated by the communication slave for sending over the field busnetwork. This will be discussed in further detail below.

In one construction, the BCCSCM 48 for each compressor 14 furtherincludes a switch device 64. The switch device 64, in one construction,is a three pole solid state relay such as SSRD Series panel mount heavyduty solid state AC relay. The SSRD Series is made by Teledyne, Inc. ofLos Angeles, Calif. and available from Allied Electronics of O'Fallon,Mo. The relay operates, upon receiving a command from the processor 49(or processor 1503), to block at least two of the three phases of theelectrical power to the compressor motor 32, thereby turning the motoroff. It is to be understood that other switch devices can be used. Theprocessor 49 is programmed to cause the relays to turn off thecompressor (14) when a safety limit value of one of the safetyparameters is traversed.

In another embodiment, the SSRD is constructed to include an overcurrentprotection capability. A current sensor (shown as current sensor 1540 inthe BCCSCM 1500), which can be associated with the switch device,monitors the current through the SSRD. If the sensed current exceeds athreshold (e.g., 350A for 1.5 line cycles), the SSRD is shut off(rendered non-conducting) to protect the compressor motor 32. Such anovercurrent condition can occur, for example, if the rotor of thecompressor motor 32 locks. Thus, a current sensor associated with theSSRD serves as a locked rotor detector. The sensed current informationmay also be used to detect other compressor abnormalities.

A current sensor that is a self-contained part of thecompressor-controlling device provides certain benefits. For example,current information is available on the system control bus via theBCCSCM for use in safety and control applications, and the value of thecurrent can be used for energy management/monitoring functions. Thecurrent sensor may be constructed internal to the SSRD, or it may be asensor external to the SSRD. For example, a current sensing toroid couldbe used external to the SSRD to sense current. Alternatively, a highpower, current sensing resistor may be included within the SSRD to sensecurrent.

FIG. 6 is a schematic representation of another aspect of an SSRD. Atypical commercial refrigeration compressor system uses three-phaseelectrical power. Thus, by controlling the SSRD, the application ofphases A, B, and C of such a three-phase power system is alsocontrolled.

As illustrated in the construction of FIG. 6, the SSRD includes threeopto-isolators 102, 104, and 106 that are constructed as an integralcomponent of the overall SSRD assembly. Opto-isolator 102 is associatedwith phase A, opto-isolator 104 is associated with phase B, andopto-isolator 106 is associated with phase C. The opto-isolators 102,104, and 106 detect the zero-crossing of the respective phases withwhich they are associated. Thus, when phase A crosses zero,opto-isolator 102 produces an output, via its collector, on line 108.Likewise, when phase B crosses zero, opto-isolator 104 produces anoutput on line 110. Similarly, when phase C crosses zero, opto-isolator106 produces an output on line 112. As one skilled in the art canappreciate from the foregoing, such zero-crossing information amounts tophase reference information, which may be compared to determine therelationship between the power phases.

As those skilled in the art will also appreciate, if power is applied tothe compressor motor 32 when an improper phase relationship exists, thecompressor motor 32 may be damaged or destroyed. For example, if ascroll compressor is run backwards, for even an instant, because of animproper phase relationship, the compressor may be seriously damaged orruined. The zero-crossing detection capability of the SSRD shown in FIG.6 is integral to the SSRD and available when the SSRD isopen-circuited—when it is non-conducting and no power is applied to thecompressor motor 32. Hence, a BCCSCM with the SSRD shown in FIG. 6 canmonitor the phases for a proper polarity relationship before applyingpower to the compressor motor 32. Stated differently, a BCCSCM with theSSRD shown in FIG. 6 can determine the presence of an improper phaserelationship by comparing the phase information to an acceptabilitystandard and prevent potential damage to the compressor motor 32 thatwould otherwise occur if power were applied to the motor. In contrast,prior art phase polarity detection schemes rely on devices external tothe SSRD. Such prior art schemes do not detect an improper phaserelationship before applying power. Rather, such systems check the phaserelationship only after power application. In such systems, if animproper phase relationship is detected, power is removed. As thoseskilled in the art can appreciate, the compressor motor 32 may bedamaged or destroyed before power is removed, even if it is removedrelatively rapidly. Thus, the SSRD, as shown in FIG. 6 (and as shown as1560 in FIG. 15), provides for phase detection prior to the applicationof power.

Referring again to FIG. 1, a master controller 70 (also referred to as asystem controller) for controlling all of the compressors 14A, 14B, and14C of the refrigeration system is in electronic communication with allof the BCCSCMs 48 of the refrigeration system via line 80. In oneconstruction, the controller 70 includes a CPU 72 (or simply aprocessing unit) which coordinates data transfer among the components ofthe system. The CPU 72 also processes data acquired from the BCCSCMs 48and determines control commands to be sent to the BCCSCMs. Other logicdevices can be used in place of the CPU 72 to perform the function ofthe CPU 72.

In one specific construction, the CPU 72 includes a 16-bit RISCprocessor, has 64 kilobytes of read only memory (ROM), 16 kilobytes ofrandom access memory (RAM), a real time clock to perform time-basedcontrol functions, and at least two interfaces (e.g., serial interfaces)to permit connection to a local human-machine interface (hereinafter,“HMI”), as well as a remote interface. The local and remote interfacesmay also be referred to herein as input/output devices. The CPU 72 canalso include both digital and analog inputs and outputs, and is poweredby a 24-VDC power supply 74 transformed and rectified from a 120-VACfeed line 69.

The controller 70 further includes a communications module 76 to permitthe CPU 72 to work with a field bus networking system. The field busnetworking system is designed to connect sensors, actuators, and othercontrol equipment (e.g., BCCSCM 48) at the field level. An example of asuitable field bus networking system is the AS-Interface® (or AS-i)networking system. Components for the AS-i network are sold commerciallyby Siemens Aktiengesellschaft of Germany, and available in the UnitedStates from Siemens Energy Automation and Control, Inc. of Batavia, Ill.The communications module 76 can be powered by the same 24-VDC powersupply 74 used by the CPU 72.

In one construction, the controller 70 includes a network power supply78, which provides a 24-VDC to 30 VDC power supply connected to the120-VAC feed line 69. The network power supply 78 provides power to thefield bus network via line 79 as further discussed below.

In one construction, the field bus network includes an unshielded twowire bus 80 connecting the communications module 76 (and hence the CPU72) to all of the BCCSCMs (and, as discussed below, other controlmodules). One wire is a ground wire and the other is a communication andpower line which carries all communication and power for the BCCSCMs 48.Power for the BCCSCMs is supplied from the network power supply 78through line 79, which has a communications decoupling feature allowingcommunications and power to be supplied over the same line. The BCCSCMs48 are each connected to the bus 80 at nodes 82 by a respective couplingthat penetrates insulation of the bus cable and makes contact with thewires. Each BCCSCM 48 is plugged into the coupling to connect thecontrol and safety module to the network.

In the construction shown in FIG. 1, the master controller 70 alsocontrols cycling of the condenser fans 22. For example, the mastercontroller 70 can monitor discharge pressure and liquid refrigeranttemperature to determine when to cycle the condenser fans 22. Similarly,the master controller 70 can monitor discharge pressure and outdoorambient temperature to determine whether to split the condenser.

In the illustrated construction, the master controller 70 transmitsthese cycling commands from the CPU 72 to a condenser controller 84located close to the fans 22. The condenser controller 84 executes thecommands for shutting down or energizing the condenser fans 22. Becausethe condenser is, in some constructions, located remotely from thecompressor rack, it may be undesirable or impractical to locate thecondenser controller 84 on the same field network bus (e.g., AS-i bus)as the CPU 72. FIG. 1 illustrates such a situation, in which thecondenser controller 84 has its own field bus network (e.g., anotherAS-i bus 85). In other words, the condenser controller 84 can have itsown field bus network for controlling the condenser fans, just like thenetwork of the compressors 14A, 14B, and 14C with the master controller70. For example, the CPU 72 can communicate with the condensercontroller 84 over a relatively longer distance network. The MultipointInterface or “MPI”, available from Siemens, is an example of such alonger distance network/field bus. Another example is the ProfiBUSstandard. In this way, the condenser controller 84 acts as a gateway toextend the range of the master controller 70 in a situation in which theprimary field bus network associated with the compressor rack could notpractically be used. Thus, the master controller 70 provides operatingand control functions to the condenser controller 84. The condensercontroller 84, via its own field bus network 85, supplies the controlinformation to a BCFCM 86 which drives the fans 22. Likewise, dataavailable at the condenser (e.g., an ambient air temperature associatedwith the condenser and information regarding which fan(s) is/are on) maybe transmitted to the master controller 70. In one construction, an airtemperature sensor provides ambient air temperature data directly to thecondenser controller 84 (i.e., independently of any field bus network),which transmits such data to the master controller 70.

Advantageously, if the master controller 70 ceases communications withthe condenser controller 84, the condenser controller is preferablyprogrammed to independently determine and provide at least some of thecontrol information required to drive the fans 22 via the BCFCM. Othercondenser control arrangements may be used. For instance, the condensercontroller 84 could be eliminated and its functions programmed into themaster controller.

The BCFCM 84 includes, in one construction, a communication slavecontroller and a microprocessor and memory as described in connectionwith the BCCSCM 1500 of FIG. 15. However, the BCFCM would includedifferent inputs and outputs connected to the microprocessor of theBCFCM than the microprocessor 1505. In other words, the inputs andoutputs connected to the microprocessor of the BCFCM would be the inputsand outputs associated with the condenser 20.

Referring now to FIG. 4, in one operation of the refrigeration system,the sensors 50–62 or 1525–1545 of each BCCSCM 48 or 1505 (e.g., theBCCSCM associated with compressor 14A) provide information regarding theoperating parameters monitored by the sensors. The information providedby the sensors 50–62 or 1525–1545 could be limited to whether or not apre-set safety limit value has been traversed. However, in oneconstruction, at least some of the sensors provide signals to theprocessor of each BCCSCM 48 or 1500 indicative of the actual value ofthe operating parameter at the time sampled.

In one construction, the sensors for discharge pressure 50 andtemperature 52, and suction pressure 54 and temperature 56 providedigital signals to the processor 49 indicative of the actual value ofthe parameter measured. Thus, the sensor/transducer converts the analogdata to a digital format before providing the information to theprocessor 49.

In the construction shown in FIG. 15, the sensors 1525, 1530, and 1535are dual function pressure/temperature sensors having an addressable, 14bit analog to digital converter. That is, each sensor includes a firstsensing device (e.g., thermistor) that senses a temperature and a secondsensing device (e.g., a strain gauge) that senses a pressure. Both thefirst and second sensing devices are disposed within a single housing.The A/D converter is also located within the sensor housing and convertsthe analog signals from the detecting devices to a single digital signalconveying the measured parameters. The A/D converter can include otherchannels (e.g., a channel for monitoring the supply voltage to thesensors), and the digital signal can convey information relating to theother channels. Additionally, the digital signal can send an error codeto the processor 1503 when an error code occurs at the sensor. Forexample, if the A/D converter does not receive a signal from thetemperature sensing device, it can generate an error code that iscommunicated to the processor 1503. The processor 1503 can thencommunicate to the system controller that a sensor error has occurred.An example dual function pressure/temperature sensor is a ML 200 psisper SCD 1126, part no. 9310101 manufactured by Honeywell.

The motor winding temperature sensor 58, and the current and voltagesensors 1540 and 1545 provide an analog signal to the processor 1505indicative of the actual value of the parameter measured. The oil levelsensor 60 (or 1555) provides a circuit open or circuit-closed signal tothe processor indicative of whether an oil level safety limit has beentraversed. The high pressure cut out 1550 provides a circuit open orcircuit-closed signal to the processor indicative of whether a pressurelimit has been traversed.

As explained above with respect to FIG. 6, phase loss or phase reversalcan be monitored/detected by monitoring the zero crossings of each phasewith a plurality of opto-isolator devices. An alternative, separatepower phase monitoring device 62 may also be used. Such a separate powerphase monitoring device 62 would, for example, provide a circuit open ora circuit closed signal to the microcontroller to indicate whether aphase loss or phase reversal has occurred.

The processor 49 or 1503 of each BCCSCM 48 or 1500 checks the inputsfrom each sensor to determine whether a safety limit value for any ofthe measured compressor characteristics has been exceeded. If no safetylimit values are exceeded, the processor 49 loads the sensor data fortransmission to the master controller 70 when the processor is queried.The master controller 70 is the system network controller in standardoperation of the refrigeration system shown in FIG. 1. In theillustrated embodiments, the host controller (or the microprocessor1505) stacks the information to await transmission to the mastercontroller 70. The processor 49 (or 1503) then waits for a message fromthe master controller 70 containing commands and a query for the sensordata. As soon as the message is received, the processor 49 responds overthe communication and power line of the two-wire bus 80 to thecontroller 70 with the information data stored from the sensors 50–62.

For the construction shown in FIG. 1, data from all of the processorsflows in a stream over the communication and power line of the bus 80 tothe communication module 76 and thence to the CPU 72 of the mastercontroller 70. The communication protocol allows the CPU 72 to associatethe operating parameter information received with particularcompressors, and to discriminate between different operating parametersfor each compressor. In one construction, more specifically, each BCCSCMis assigned a particular address, which allows the controller 70 tocommunicate individually with each of the BCCSCMs over the same line,and also allows the BCCSCM processors to identify themselves to themaster controller.

The data is now available through interfacing with the master controller70, either remotely or by a local human machine interface, to viewindividual compressor data. The processor 49 (or 1503) also looks forthe command portion of the master controller 70 message for a command toturn the compressor (14A, 14B, or 14C) on or off. If such a command ispresent, the processor 49 executes it by operating the solid state relay(switch device 64) to turn the compressor on or off. However, if thecommand is to turn the compressor on, the processor 49 will not executeit if the processor 49 has previously determined that a safety limitvalue of one of the safety parameters has been traversed and remains ina safety exception state. It is envisioned that other capacity controlcommands could be received and executed by the processor 49 such as whenthe compressor was of a variable capacity type. The software of theprocessor then returns to the initial step of reading the sensor inputs.

Before proceeding further, another method of communication between themaster controller 70 and the BCCSCM 1500 (or 48) will now be discussed.The method below will be described for the master controller 70 incommunication with the BCCSCM 1500 via an AS-i cable (i.e., bus 80);however, other networks can utilize the method below. For example, othernetworks that do not utilize an AS-i bus can implement the method.

The communication slave 1520 shown in FIG. 15 is an AS-i compatible ASICthat is in communication with the communication module 76 (referred tobelow as the master). The communication module 76 is or includes an AS-icompatible ASIC. The communication slave 1520 is in furthercommunication with the microprocessor 1505. More specifically, thecommunication slave 1520 and the microprocessor 1505 are electricallycoupled by four “control” (or “parameter”) channels P0, P1, P2, and P3;four “output” channels DO0, DO1, DO2, and DO3; four “input” channelsDI0, DI1, DI2, and DI3; a DSR channel; and a PST channel. Each channelP0, P1, P2, P3, DO0, DO1, DO2, DO3, DI0, DI1, DI2, DI3, DSR, and PST iscoupled to the communication slave 1520 at a respective terminal. Otherconfigurations can be utilized for the communication method describedbelow. For example, the method is not limited to four “input” or four“output” channels. Additionally, other devices can be used in place ofthe master ASIC, slave ASIC, and the microprocessor.

The AS-i networking solution was originally designed to control fouractuators (relays, solenoids, etc.) and/or read four switched inputs. Tocontrol the four actuators, the AS-i master transmits requests via thetwo-wire interface, which also carries the 30 VDC power, to the AS-islave. In response to the master requests, the AS-i slave eitherswitches its outputs to the state directed by the AS-i master orresponds to the master with the current state of its inputs. Inaccordance with this communication activity, four data bits representingthe desired output state or current input state are transmitted duringeach master-request/slave-response communication cycle. The AS-i slavecan also use parameter bits to define or control operation of theattached slave (e.g., to logically AND or OR with the otherinputs/outputs). A data exchange with the AS-i slave causes the datastrobe output DSR to pulse, while a parameter write to the AS-i slavecauses the parameter strobe PST to pulse.

For communication between the communication module 76 and the BCCSCM1500, a redefinition of the use of the inputs and outputs of the slave1520 allows the slave 1520 to be connected to a microprocessor as acommunication gateway via the AS-I bus. When coupled in this fashion,the slave/microprocessor 1520/1505 combination creates an AS-i busaccessible slave device capable of communicating variable length dataelements from an addressable array of bytes. Further, by defining someof the available addressable bytes as pointers into the microprocessormemory space, additional data space is available for transmission overthe AS-i bus.

The AS-i protocol calls for communication between the AS-i master andAS-i slave to be in four-bit data packets. That is, each request orresponse across the AS-i bus includes a wholly self-contained message offour-bits. Please note, however, each request and response can includeother bits (e.g., addressing bits, parity bit(s), etc.) forcommunication between devices on the network.

Generally speaking, a master request controls the output states of theoutput terminals P0–P3 or DO0–DO3 and the AS-i slave 1520 responds byincluding the states of the inputs DI0 and DI3. The control (orparameter) bits P0–P4 provide additional information to themicroprocessor. The P0 and P1 bits are data block selection bits(discussed below), the P2 bit is a read/write selection bit, and the P3bit is a compressor ON/OFF bit. The microprocessor 1505 monitorsactivity on the communication channels with the slave 1520 and controlsthe inputs to the slave 1520.

The microprocessor is coupled to a 256-bit memory. The 256-bit memory isdivided into four, eight-byte blocks. When writing to or obtaining datafrom the 256-bit memory, the P0 and P1 bits select one of the blocks.Therefore, the number of blocks (2^((m)) blocks) can vary if the numberof selection bits (m) varies. FIGS. 22A, 22B, 22C, and 22D represent oneconfiguration for the four blocks 2210, 2220, 2230, and 2240.

Each block is further divided into sixteen sub-blocks. For theconstruction shown in FIGS. 22A–22D, each sub-block includes four-bits(or a nibble). The size of each sub-block (e.g., (n) bits) is equal tothe number of input/output channels (e.g., (n) channels). The totalnumber of sub-blocks in a block is equal to 2^((n)), and a binary numberfrom 0 (e.g., 0000) to 2^((n)) (e.g., 1111) identifies each sub-block.However, other configurations are possible.

Referring to FIGS. 22A–22D, each sub-block contains one or more piecesof information (e.g., one or more parameters), one or more sub-blockscan be combined to form a piece of information (e.g., form a parameter),one or more sub-blocks can be used as a pointer, or a sub-block can beunused. For example, block 2240 uses sixteen nibbles for storing sixparameter values. More specifically, nibbles 0000 and 0001 (byte 0)represent a value for the “suction pressure cut in” parameter; nibbles0010 and 0011 (byte 1) represent a value for the “suction pressure cutout” parameter; nibbles 0100 and 0101 (byte 2) represent a value for the“split suction assignment” parameter; nibbles 0110, 0111, 1000, and 1001(bytes 3 and 4) represent a value for the “discharge pressure limit”parameter; nibbles 1010, 1011, 1100, and 1101 (byte 5 and 6) represent avalue for the “discharge temperature limit” parameter; and nibbles 1110and 1111 (byte 7) represent a value for the “oil pressure limit”parameter. As another example, nibbles 1110 and 1111 (byte 7) of block2210 include values for eight parameters. As yet another example,nibbles 1110 and 1101 (byte 6) of block 2220 is unused in theconfiguration shown.

In the construction shown in FIG. 22, bytes 0 and 1 of block 2230include a 16-bit pointer. The 16-bit pointer points to data stored inRAM 1510. The resulting value corresponding to the pointer is stored inbytes 2 and 3 of block 2230. By using the pointer, additional storagecapabilities can by used at the processor 1503. Other pointers, pointersizes, and data sizes can be used. Also, it should be noted, that thedata blocks 2210 to 2250 are mirrored at the master controller 70.

Because there is only a four-bit control architecture, the network usesan operation sequence for reading and writing data of particular length.FIG. 23 includes a flow diagram representing a read sequence. At 2300,the AS-i master issues a “write_parameter” message to the AS-i slave1520. The “write_parameter” message includes a two-bit value forselecting a data block, a one-bit value for informing the processor 1503a read operation is beginning, and a one-bit value for the currentcompressor state. The “write_parameter” message is then communicatedfrom the communication slave 1520 to microprocessor 1505 on channelsP0–P3.

At block 2305, the master issues a “data_exchange” message to the slave1520. The “data_exchange” message includes a four-bit value pointing toone of the sixteen nibbles of the selected block. The “write_parameter”message is then communicated from the communication slave 1520 to themicroprocessor 1505 on channels DO0 to DO3.

At block 2310, the microprocessor 1505 responds by obtaining the storedbits of the identified nibble, and communicating the obtained bits tothe slave 1520 on channels DI0 to DI3. The slave then communicates theobtained nibble to the master in the next state change. At block 2320,the master controller 70 stores the obtained nibble in its mirrored256-bit storage.

At block 2325, the master controller determines whether all nibbles forthe requested parameter have been obtained. If the result isaffirmative, the master controller combines the stored nibbles (ordivided if the parameter is less than a nibble), resulting in therequested parameter value. If the result is not affirmative, then thenetwork repeats blocks 2305, 2310, 2320 and 2325. Therefore, the networkdecomposes, transmits, and composes variable length data in four-bitpackets.

FIG. 24 includes a flow diagram representing a write sequence. At 2400the master controller decomposes a message to be communicated to themicroprocessor 1505 into a plurality of nibbles (or creates a nibble ifa message is less than a nibble). At 2403, the AS-i master issues a“write_parameter” message to the AS-i slave, which is then communicatedto the microprocessor 1505 on channels P0–P3. The “write_parameter”includes a two-bit value for selecting a data block, a one-bit value forinforming the processor 1503 a write operation is beginning, and aone-bit value for the current compressor state.

At block 2405, the AS-i master issues a “data_exchange” message to theAS-i slave 1520, which is then communicated to the microprocessor 1505on channels DO0 to DO3. The “data_exchange” message includes a four-bitvalue pointing to one of the sixteen nibbles of the selected block. Theslave responds with a dummy value, which is ignored (block 2405).

At block 2410, the AS-i master issues a second “data_exchange” messageto the AS-i slave 1520, which is then communicated to the microprocessor1505 on channels DO0 to DO3. The second “data_exchange” message includesa four-bit value that is written to the selected nibble. The slaveresponds with a dummy value, which is ignored (block 2418). At block2420, the master controller determines whether all nibbles for therequested parameter have been communicated. If the result isaffirmative, the master controller exits the write routine. If theresult is not affirmative, then the network repeats blocks 2405, 2408,2415, 2418 and 2420. Therefore, the network decomposes, transmits, andwrites variable length data in four-bit packets.

Referring again to the constructions shown in FIGS. 1, 2, and 15, whenone or more of the inputs from the sensors 50–62 (or 1525–1555) to theprocessor 49 (or 1503) traverses a safety limit value, the processor 49,for these constructions, loads a safety exception message for the mastercontroller 70 and immediately shuts down the compressor (e.g.,compressor 14B). The safety exception message is loaded into the top ofthe stack of information to be sent to the master controller. When theprocessor 49 receives a message from the master controller 70, itresponds by including the safety exception message for the mastercontroller. The master controller 70 knows not only that one of thesafety limit values for a particular compressor was traversed, but whichsafety parameter or parameters were traversed and in most instances theactual values of those parameters. An alarm can be activated by themaster controller 70 to alert the appropriate persons that a problemexists. The information can be accessed by a technician via a suitableHMI in the system (located, for example, at the controller 70), orremotely such as through an Internet connection. The informationregarding the operating parameters of the properly functioningcompressors (e.g., 14A, 14C) can also be accessed in this manner.

In some constructions, the BCCSCM 1503 (or 48) includes digital sensors.If a sensor is a digital sensor, the digital sensor can communicate acode indicating a fault has occurred at the sensor. Alternatively, thedigital value or voltage received from the sensor can indicate faultywiring (e.g., an open or short circuit) or a faulty transducer. Similarto what was discussed above, the processor 1503 (or 49) can load amessage for the master controller 70 informing the controller of thesensor error. The message is loaded into the top of the stack ofinformation to be sent to the master controller 90. When the processor1503 receives a message from the master controller 70, it responds byincluding the message for the master controller. An alarm can beactivated by the master controller 70 to alert the appropriate personsthat a problem exists. Other control modules (discussed below) canoperate similarly.

In some constructions, the compressor having a faulty sensor maycontinue to operate. For example, in one construction, each BCCSCM 1500includes sensors that sense, among other things, suction pressure.Theoretically, the suction pressure for each compressor 14 attached tothe same suction header should have the same pressure (but practically,may slightly differ due to filters and pipe length). If one of thecompressors (e.g., compressor 14A) has a faulty suction pressure sensor,the master controller 70 can use the sensed suction pressure of theother compressors (e.g., 14B and/or 14C) attached to the same suctionheader (e.g., suction header 16) as the compressor (e.g., 14A) havingthe faulty sensor to control that compressor (e.g., 14A). Alternatively,the system can include a pressure sensor coupled to the suction header16 (or piping in communication with the suction header) to controloperation of a compressor having a faulty sensor. In addition to usingthe redundant value at the master controller 70, the master controllercan communicate the redundant value to the BCCSCM having the faultysuction pressure sensor. Therefore, the refrigeration system can use theredundancy of the attached sensing devices to continue operation of acompressor (or other subsystem) having a faulty sensor, even though thecompressor (or other subsystem) includes the faulty sensor.

Before proceeding further, it should be noted that, although the failedsensor was a sensor that measures suction pressure, the system canperform similarly for other sensors (e.g., suction temperature,discharge pressure, discharge temperature, etc.) and for other sensorsattached to other control modules (discussed below). Additionally, themaster controller 70 can compare values acquired from sensors thatshould have similar or substantially similar values to determine whetherone of the sensors is faulty (e.g., a faulty sensor due to drift).Continuing the above example, the master controller 70 can compare thesensed suction pressure for compressors 14A, 14B, and 14C. If one of thesensed values (e.g., the suction pressure for compressor 14A) issignificantly different than the values of the other compressors (ordifferent than a sensor attached to the suction header 16), then themaster controller 70 can mark the suction pressure sensor having thesignificantly different value as faulty. An alarm can be activated bythe master controller 70 to alert the appropriate persons that a problemexists. Additionally, the master controller can communicate the fault tothe compressor having the faulty sensor.

As discussed herein, the master controller 70 receives informationconcerning operation parameters of the compressors 14A, 14B, and 14C. Aprimary control parameter is suction pressure. The controller 70 isprogrammed so that it manipulates (e.g., such as by averaging) thesuction pressure readings from the BCCSCMs 48 to determine therefrigeration level produced by the multiplexed compressors 14A, 14B,and 14C. The controller 70 uses this information to strategize cyclingcompressors in the system to achieve the desired refrigeration capacitylevel.

One exemplary method of dynamically controlling a plurality ofmultiplexed compressors (e.g., compressors 14A, 14B, and 14C) isschematically shown in FIGS. 16A–16F. The flowcharts represent one ormore software modules that are continuously called by the CPU 72 todynamically control the multiplexed compressors. Before proceedingfurther, it should be noted that the blocks of FIGS. 16A–16F representsoftware instructions received, interpreted, and executed by the CPU 72,resulting in the CPU 72 (and the master controller 70) performing theoperations of the blocks. It should also be noted that FIGS. 16A to 16Fis one exemplary method. Other acts can be included with the methodshown in FIGS. 16A–16F, one or more acts shown in FIGS. 16A–16F can beremoved, and the order or sequence of the acts shown in FIGS. 16A–16Fcan vary. Furthermore, while the method shown in FIGS. 16A–16F will bedescribed in connection with software, the method can be implemented byother means (e.g., an ASIC).

As discussed earlier, the refrigeration system includes one or moremultiple suction groups, where each suction group has one or morecompressors. If a suction group has a plurality of compressors, thecompressors are multiplexed in an arrangement (typically a parallelarrangement). Referring to FIG. 16A, the master controller 70 performs acapacity calculation for each suction group and each compressor of eachsuction group. At blocks 1600, the master controller 70 initializes theloop counters. At blocks 1605, the master controller 70 determines(e.g., calculates by adding capacities for each compressor (as shown inFIG. 16A), obtain previous calculations from storage, etc.) the totalcapacity for the suction group at a given operating point. The mastercontroller 70 uses known equations for determining the capacity of eachcompressor at the current operating pressures when performing thecapacity calculations. At blocks 1610, the master controller 70determines the capacity of each individual compressor as a percentage ofthe total capacity. By way of example, if a first suction group hasthree compressors (e.g., 14A, 14B, and 14C), the first compressor (e.g.,14A) may have a 50% capacity, a second compressor (e.g., 14A) may have a25% capacity, and a third compressor (e.g., 14A) may have a 25%capacity. At block 1615, the master controller determines whether thecapacity calculations were performed for all of the suction groups. Ifthe answer is affirmative, then the master controller proceeds to block1620 (FIG. 16B). Otherwise, the master controller returns to block 1605.

At FIG. 16B, the master controller determines a current compressor runpattern, current run capacity, and current % total capacity. At blocks1620, the software initializes the loop counters. At blocks 1625, themaster controller 70 builds a binary image of the status of thecompressors 14 and determines the current run capacity of each suctiongroup. More specifically, the master controller 70 determines whichcompressors 14 are currently on, and adds the capacity of each activatedcompressor 14 to the current run capacity for the respective suctiongroup(s). At block 1630, the master controller 70 determines the currentrun capacity of each suction group as a percentage of the total capacityof each suction group. Continuing the earlier example, if the second andthird compressors 14B and 14C are ON, then the current run capacity is50% of the total capacity. At block 1635, the master controllerdetermines whether the capacity calculations were performed for all ofthe suction groups. If the answer is affirmative, then the mastercontroller proceeds to block 1640 (FIG. 16C). Otherwise, the mastercontroller returns to block 1620.

In FIGS. 16C–16F, the master controller 70 determines the controlpattern for the next cycle. At block 1645, the master controller 70determines whether an increase in run capacity is required. If theanswer is affirmative, then the master controller proceeds to block 1650(FIG. 16D). Otherwise, the master controller proceeds to block 1655(FIG. 16E).

With reference to FIG. 16D, the master controller 70 determines the nextcontrol pattern, which requires an increase in run capacity. Increasingthe run capacity of a suction group typically requires activating aninactive compressor. At block 1650, the master controller determineswhether all compressors are ON. If the answer is affirmative, then themaster controller proceeds to block 1660 (FIG. 16C). Otherwise, themaster controller proceeds to blocks 1665 (FIG. 16E). At blocks 1665,the master controller 70 determines each available capacity percentagecombination for each suction group. Continuing the earlier example, thepercentage combinations for compressors 14A, 14B, and 14C include 25%,25%, 50%, 50%, 75%, 75%, and 100%. However, if one of the compressorshas an alarm condition, that compressor is removed from the possiblecombinations (block 1665E). At blocks 1670, the master controller 70determines the next capacity increment. Revisiting the earlier example,the second and third compressors 14B and 14C were ON resulting in a 50%run capacity. The next available run capacity is 75% (i.e., activatingthe first compressor 14A with either the second or third compressors 14Bor 14C). At block 1670F, the master controller 70 performs a “FIFOtest.” The FIFO test (shown in detail in FIG. 16F) determines the nextcompressor run pattern when multiple possible combinations have anequivalent run capacity. That is, if blocks 1665 and 1670 result inmultiple combinations for the next available capacity, the FIFO testdetermines the next compressor run pattern. Continuing the earlierexample, the next available run capacity for the three compressors 14A,14B, and 14C is 75%, and there are two combinations that result in thatrun capacity (i.e., compressors 14A and 14B, or compressors 14B and14C). In the configuration shown in FIG. 16F, the master controller 70selects the most optimal run pattern for the compressors 14. Forexample, the most optimal run pattern can include compressor run time asa variable. Optimizing the run pattern with compressor run time attemptsto equitably distribute compressor run time over the compressors of thesuction group. However, other tests can be included in selecting thenext compressor run pattern.

Returning to block 1645, the master controller determines whether anincrease in run capacity is required. If the answer is negative, thenthe master controller 70 proceeds to block 1655 (FIG. 16E). In general,the control scheme of FIG. 16E corresponds to FIG. 16D; however, themaster controller 70 decreases the run capacity of the suction group.Decreasing the run capacity typically requires deactivating an activecompressor.

At block 1655, the master controller 70 determines whether allcompressors 14 are OFF. If the answer is affirmative, then the mastercontroller 70 proceeds to block 1660 (FIG. 16C). Otherwise, the mastercontroller 60 proceeds to blocks 1675 (FIG. 16E). At blocks 1675, themaster controller 70 determines each available percentage combinationfor each suction group. Blocks 1675 generally correspond to blocks 1665(FIG. 16D). At blocks 1680, the master controller determines the nextcapacity decrease. Revisiting the earlier example, the first and secondcompressors were ON resulting in a 50% run capacity. The next availablerun capacity decrement is 25% (i.e., activating the second or thirdcompressors 14B or 14C). Similar to 1670 discussed above, at block1680F, the master controller 70 performs a “FIFO test.” The FIFO test(shown in detail in FIG. 16F) determines the next compressor run patternwhen multiple possible combinations have an equivalent capacity. Thatis, if blocks 1675 and 1680 result in multiple combinations for the nextavailable capacity, the FIFO test determines the next compressor runpattern. Continuing the earlier example, the next available capacity forthe three compressors 14A, 14B, and 14C is 25%, and there are twocombinations that result in that capacity (i.e., activating the secondor third compressors 14B or 14C). In the configuration shown in FIG.16E, the master controller selects the next compressor run pattern.

Returning back to blocks 1660 (FIG. 16C), the master controller 70updates sequence status information in view of FIFO calculations. Morespecifically, the master controller keeps a continuous runtime for eachcompressor 14A, 14B, and 14C. This information is used in the FIFOcalculations when multiple capacities are possible. At block 1685, themaster controller 70 exits the software routine, resulting in a patternfor each suction group.

In one construction, the routine shown in FIG. 16 is called when achange in capacity for a suction group is required. More specifically,in one construction of the refrigeration system, a PID error signal isused for controlling the operation of the compressors 14. If the errorsignal requires a change in capacity, the CPU 72 invokes the routine inFIG. 16, resulting in a new run pattern.

In one construction, should the master controller 70 (and in particularthe CPU 72) fail, the BCCSCMs 48 and 1500 are capable of performing thecontroller functions for the compressors 14A, 14B, and 14C. A flowchartof the one operation of the processors 49 (or 1503) in the master failmode is shown in FIG. 5. As stated above with reference to FIG. 4, theprocessor 49 of each BCCSCM 48 waits a predetermined time period for amessage from the master controller 70. If the period times out with nomessage, the processor 49 defaults to a master fail operation mode.

In the operation shown in FIG. 5, the BCCSCMs 48 (and/or 1500)communicate with each other over the communication and power line of thebus 80, in addition to communicating with the controller 70. In thefailure mode, each processor 49 (or 1503) determines whether it is tohave primary control. One processor of the BCCSCMs will have previouslybeen programmed with a certain identification or address, e.g., ID=1.Typically, this would be the BCCSCM 48 of the first compressor 14A inthe system. Any BCCSCM 48 not having this identification will continueto operate only responsively to commands received over the field busnetwork (i.e., it resumes standard operation as a slave). It is alsoenvisioned that the slave processors (i.e., processors associated withcompressors 14B, 14C) would start a second timer once entering thefailure mode to look for a message from the processor of the BCCSCM 48designated for primary system control in the failure mode (i.e., theprocessor 49 associated with compressor 14A). If the other processors 49do not receive such a message, a second BCCSCM 48 would be pre-selected(e.g., the BCCSCM having ID=2 associated with compressor 14B) to controlthe operation of the system in the failure mode. Thus, the system ishighly granular, allowing for multiple failures while maintainingoperation.

In one method of operation, the processor 49 (or 1503) of the BCCSCM 48(or 1500) of compressor 14 is identified as the primary control ormaster, in case of failure of the master controller 70, and will executea master control function involving at least basic compressor cycling.In that regard, the primary control processor 49 is capable ofdetermining the collective suction pressure of the operating compressors14A, 14B, and 14C and providing control commands for itself and theother slave processors to turn compressors on and off to maintain therefrigeration capacity requirements of the system. After performing thisfunction, the “primary” processor 49 resumes a slave presence on thenetwork which allows it to again look for a message from the mastercontroller 70 for a period of time before returning again to perform asystem control function. Once the master controller 70 is detected, theprimary control processor 49 returns to its standard (slave) mode ofoperation.

In general, the distributed intelligence control provides for ease ofassembly and installation and enhances control. The compressors 14A,14B, and 14C are configured with one or more sensors to optimizeuniformity of measurement of operation parameters and to minimizeinstallation variances as well as provide protection of such sensordevices. The modularity and intelligence of the compressor controllersinterface with the master controller 70 to assure optimum compressorperformance, as well as granularity of the system.

For the constructions utilizing a two wire bus that provides power andcommunication to the control modules (e.g., via an AS-i bus), assemblyof a refrigeration system is made easier by simplification of the wiringwhich is normally done upon installation. The high voltage lines 44A,44B, and 44C are still used to run the compressors 14A, 14B, and 14C forprimary operation. According to electrical codes, it is typicallyrequired to shield these lines such as by placing them in conduit.However, for the construction shown in FIG. 1, no separate power linesother than three phase high voltage lines 44 must be run to thecompressor motors 32. Additionally, it is unnecessary to run additionalhigh voltage lines to the BCCSCM's. Instead, a single high voltage feedline 69 supplies the power supply 74 for the CPU 72 and communicationmodule 76 and also the network power supply 78.

Power for all of the BCCSCMs 48 (and/or 1500) is supplied through thesame two wire bus 80 extending from the communications module 76 to thecontrol and safety modules 48. The bus 80 does not need to be shieldedbecause it carries only 30 VDC power. Preferably, the wiring of theBCCSCMs 48 to the master controller 70 is done at the factory where thecompressors 14A, 14B, and 14C are mounted together with the controlleron a compressor rack (not shown) so that no power wiring of any kind forthe BCCSCMs is required at the building site. The number of BCCSCMs 48attached to the bus 80 up to some upper limit of the controller 70(e.g., 31) is immaterial and requires no special re-configuration of thecontroller.

As stated above, the connection of the BCCSCMs 48 (and/or 1500) to thecommunication bus 80 achieves not only power, but communications for thecontrol and safety modules. No separate feedback wiring from theindividual sensors is necessary. The processor 49 (or 1503) of theBCCSCM executes commands from the master controller 70 and is capable ofreporting back to the controller 70 that the command has been executed.The processor 49 reports the readings from all of the sensors 50–58 or1525–1555, and not only whether a safety limit value has been exceeded,but exactly which one it is and what the exact value was. This enablesthe master controller 70 to provide specific information to a repairtechnician without any additional wiring between the controller 70 andthe BCCSCM 48. In addition to permitting refrigeration level control bythe controller 70, the system allows the controller 70 to make otheradjustments in the system and to monitor trends for use in failureprediction/avoidance.

The processors 49 (and/or 1503) of the BCCSCMs also, in oneconstruction, have the embedded intelligence to operate therefrigeration system in case the master controller 70 fails. In thatregard, the BCCSCMs 48 (and/or 1500) are capable of communicating witheach other as well as the master controller 70 over the two wire bus 80.In case of failure of the master controller, one of the BCCSCMs willtake over as master or “primary” and can perform at least the functionof averaging the measured suction pressure readings from the operatingcompressors to determine refrigeration level and determine how to cyclethe compressors to maintain a predetermined capacity.

Referring still to FIG. 1, the commercial refrigeration system may alsooptionally include one or more liquid subcoolers 15 and an oilseparation and return subsystem 17. The general operation of liquidsubcoolers is known in the art. An exemplary embodiment of a controlsystem for controlling such a subcooler and/or such an oil separationand return system, in accordance with aspects of the present invention,is described in further detail below with respect to FIGS. 10 and 10A.Examples of oil separation systems are included in U.S. Pat. Nos.4,478,050, 4,503,685, and 4,506,523, which are incorporated herein byreference.

For purposes of disclosure and simplicity, the refrigeration so fardescribed herein has been, primarily, a vapor phase evaporative coolingsystem. The invention, however, is not to be so limited in itsapplication. For example, FIG. 1A is a schematic diagram of oneexemplary form of a modular secondary refrigeration system 200 whichcould also be modified to be implemented and controlled by an integrateddistributed intelligence control system. Such a secondary cooling systemis described in exacting detail in U.S. Pat. No. 5,743,102, the entiredisclosure of which is incorporated herein by reference.

Referring to FIG. 1A, the refrigeration system 200 comprises a primaryvapor phase refrigeration system including a plurality of parallel,multiplexed compressors 202. The compressors deliver liquid refrigerantat high temperature and pressure to a first condenser 204 and a secondcondenser 206 from which the liquid refrigerant passes to an expansionvalve 208 feeding the refrigerant into an evaporator 210. Vaporousrefrigerant is drawn from the evaporator 210 back to the compressors 202to complete a conventional vapor phase refrigeration cycle. However, theevaporator 210 is incorporated as part of a first heat exchangerincluding a first reservoir 212 holding a coolant liquid (e.g., glycol).Typically, this reservoir 212 is located close to the compressors andcondensers so that the vapor phase refrigerant loop is short, requiringminimal refrigerant. The first reservoir 212 is part of a secondaryrefrigeration system including pumps 214 which drive coolant fluidthrough the reservoir to second heat exchangers 216 located inrespective fixtures 218, which may constitute refrigerated merchandisersin the shopping arena of a supermarket. The coolant liquid absorbs heatfrom items (not shown) in the fixtures 218, while remaining in a liquidstate, and then is forced by the pumps 214 back to the first reservoir212 where that heat is removed to the vapor phase refrigeration system.The vapor phase refrigeration system may beneficially be, but is notnecessarily, located adjacent to the fixtures 218. The temperature ofthe fixtures 218 may be maintained through the use of sensors (e.g.,sensors 220) which control valves 222 and the pumps 214. The controlsystem, in one construction, may be beneficially used to control theoperation of the primary vapor phase and secondary liquid refrigerationsystems according to the principles set forth herein.

The refrigeration system 200 further includes a coolant liquid defrostsystem comprising a second coolant liquid reservoir 224 that containsthe first condenser 204. The coolant liquid system pumps 214 are valvedto divert some of the coolant liquid to the reservoir 224 where it isheated by the hot refrigerant passing through the first condenser 204.At a predetermined interval or when it is sensed that frost has built upon the second heat exchangers 216, valves including defrost valves 226are controlled to stop the flow of cold coolant liquid from the firstreservoir 212 to the second heat exchangers 216 and to permit flow ofheated coolant liquid to the second heat exchangers for defrosting.Again, the control system can be beneficially employed to controloperation of the defrost of the system 200. Additional aspects ofsecondary cooling systems, including specific valving and flow controlstructures, are disclosed in U.S. Pat. No. 5,743,102. Accordingly, oneskilled in the art having the benefit of the present disclosure couldadapt the teachings herein for use with secondary cooling systems byproviding similar distributed, modular control and monitoring of thecompressors, valves, set points, and other components/sensors associatedwith such secondary cooling systems.

FIG. 7 is a system block diagram illustrative of an integrateddistributed intelligence control system 700 for use in a refrigerationapplication, such as a commercial refrigeration application. As depictedtherein, the system 700 preferably includes several field buscommunication networks that cooperate to provide distributedintelligence system monitoring and control. A local network server 702,a local workstation 704, and a remote workstation 706 provide top-levelcontrol. In one construction, the local network server 702 and the localworkstation 704 will be installed near the refrigeration system (e.g.,inside the facility containing the refrigeration system). In oneconstruction, the remote workstation 706 is constructed and configuredto communicate via a wide-area network such as the Internet 708. Othernetwork levels are preferably connected to the top-level via acommunications interface, such as, for example, an Ethernet hub 712.

A first field bus control network 716, which preferably comprises anAS-i bus as previously described herein, is connected to the Ethernethub 712 via a gateway interface device 714 and a rack PLC 720 (alsoreferred to as the system controller). It is to be understood andappreciated that the rack PLC 720 illustrated in FIG. 7 corresponds tothe CPU associated with master controller 70, which is illustrated anddescribed with respect to FIGS. 1 and 2 above. Accordingly, the rack PLC720 may also be referred to as the CPU or even as the master controller.One construction of the gateway interface device 714 is a Siemens IPC,which is a Windows NT® based computer. As explained in greater detailbelow, gateway interface device 714 is constructed and arranged toprovide a gateway between similar and dissimilar field bus networkshaving similar and dissimilar network protocols. In other constructions,one or more operations described in connection with the remoteworkstation 706, the local workstation 704, and/or the local networkserver 702 can be performed by the gateway interface device 714 andvice-versa. For one exemplary construction, the device 714 can functionas both the local workstation and the gateway interface. As anotherexample, in some constructions that are discussed below, the device 714includes one or more tables for use by the rack PLC 720. However, thesetables can be located at the remote workstation 706 or the localworkstation 704.

A wireless hub 713 may optionally be included to allow access to thecontrol network by a work station over a wireless interface (e.g., awireless Ethernet link), such as between a wireless computing device 715(e.g., a Windows CE® compatible computer) and the Ethernet hub 712.

Local workstation 704, remote workstation 706, and wireless computer 715can be used to access system information such as, for example, setpoints, defrost schedules, alarm logs, current system conditions (e.g.,temperatures), and other system status and set point information.Likewise, these devices may be used to input system information such asset points or system schedules (e.g., defrost schedules or maintenanceschedules).

The first field bus control network 716 also includes an AS-i masterinterface 722 which serves as a communication interface between rack PLC720 and various control modules. The AS-i master interface 722corresponds to the communication module 76 discussed above with respectto FIG. 1. The devices associated with the first field bus controlnetwork 716 may be generally referred to as “rack devices,” or as being“located at the rack.” This nomenclature is used because in theembodiment illustrated in FIG. 7, rack PLC 720 is installed at or nearthe rack of compressors for which it provides system integration andcontrol. For example, a rack will typically include between two andthirty-one compressors, and a given installation may include multipleracks. Thus, a large system might have thirty-two racks of compressors,each controlled by a separate rack PLC that interfaces with a commonprocessor or gateway device. In one construction, each rack PLCinterfaces with computer/gateway interface device 714. The gatewaydevice 714 accommodates for set point control, status monitoring, faultlogging, data storage, and the like for each rack PLC (and the devicesintegrated by such rack PLC) in the system. For simplicity, FIG. 7depicts an installation having only a single rack, and, accordingly, asingle rack PLC 720.

Before proceeding further, it should be noted that aspects of therefrigeration system discussed herein are not limited to a refrigerationsystem having compressors located on a rack. Rather, one or more aspectsdiscussed herein can be applied to systems having a single compressorunit and to systems having multiple single compressor units not locatedon a rack.

The control modules illustrated in FIG. 7 preferably include one or morecompressor controllers (e.g., Bus Compatible Compressor Safety andControl Modules or BCCSCMs 48 or 1500), one or more branch controllers724 (also referred to herein as Bus Compatible System Branch Modules 724or BCSBMs), and one or more valve controllers 726 (also referred toherein as Bus Compatible Valve Control Modules or BCVCMs). The one ormore compressor controllers 48 (or 1500), one or more branch controllers724, and the one or more valve controllers 726 will also be genericallyreferred to herein as device controllers and subsystem controllers. Whenconnected to the first field bus control network 716, each of thesemodules 48, 724, and 726 communicates with rack PLC 720, via an AS-icompatible bus 728 and AS-i master 722. The operation of BCCSCM 48 haspreviously been described. The operational aspects of the BCSBM 724 andthe BCVCM 726 are described in greater detail below. Of course, otherconstructions for the first field bus control network 716 can by usedwith the refrigeration system. For example, other field bus types can beused in place of the AS-i compatible bus 728.

A second field bus control network 730, which can also comprise anotherAS-i bus as previously described herein, is connected to gatewayinterface 714 and the master controller (rack PLC 720) over a relativelylonger distance network 731 (e.g., a twisted pair network, such as, forexample, a Siemens' MPI compatible interface or ProfiBUS). In oneconstruction, the second field bus control network 730 is slaved to therack PLC 720. However, other configurations are possible. Second fieldbus control network 730 includes a condenser PLC 732 (also referred toas condenser controller), another AS-i master 734, and one or more fancontrol modules 736 (also referred to as Bus Compatible Fan ControlModules or BCFCMs). For FIG. 1, the condenser PLC 732 corresponds tocondenser controller 84, and may also be referred to as providing anetwork gateway between BCFCM 736 and rack PLC 720. Operational aspectsof the condenser PLC 732, AS-i master 734, and BCFCM 736 were alsodescribed above with regard to FIG. 1. Of course, other constructionsfor the second field bus control network 730 can by used with therefrigeration system. For example, other field bus types can be used inplace of the AS-i compatible bus.

A third field bus control network 740 communicates with rack PLC 720over another relatively longer distance communication bus 741, such as,for example, a LonWorks® network (also referred to as a LonWorks® bus oran Echelon network). LonWorks® information and network components areavailable from the Echelon Corporation of Palo Alto, Calif. The thirdfield bus control network 740 is used to facilitate communicationsbetween the master controller (rack PLC 720) and one or morerefrigeration cases, which are controlled by one or more case/fixturecontrollers 744 (also referred to as Bus Compatible Modular CaseControls, BCMCCs, case controllers, or display case controllers), theoperation of which is described below. Similar to the other devicecontroller introduced earlier, the one or more case/fixture controllers744 will also be generically referred to herein as device controllersand subsystem controllers. Communications between the BCMCC 744 and rackPLC 720 occurs via interface gateway 714 and the communication bus 741.The type of gateway device used will typically depend upon thebus/communication protocols employed. In the system illustrated in FIG.7, BCMCC 744 operates on a LonWorks®/Echelon compatible bus, thusinterface gateway 714 is constructed and arranged to integratecommunications between such a bus and rack PLC 720. Of course, otherconstructions for the third field bus control network 740 can by usedwith the refrigeration system.

Also, as illustrated in FIG. 7, third party controls 746 and 748 (e.g.,HVAC, fire, and rack/case controls) can optionally interface to, andbecome part of, system 700, via communication bus 741. Thus, the systemfacilitates interoperability between control systems from differentsources that are compatible with the gateway and communication standardused for the associated communication bus (e.g., AS-i, ProfiBus,LonWorks®/Echelon or Ethernet). Using distributed intelligence controlsystem 700, for example, third party controls 746 and 748 can beintegrated and used if such controls are compatible withLonWorks®/Echelon interface standards and protocols. A third partyfixture/case controller that is compatible with communication bus 741and interface gateway 714 can be used to interface with and control oneor more refrigerated fixtures (not shown) via a case/fixture controller(e.g., BCMCC 744). In one construction, the rack PLC 720 canadvantageously continue to maintain integrative control over the entiresystem by retaining knowledge over the operation of BCMCC 744.Accordingly, even when third party controls are desired or required fora part of the overall refrigeration system, the advantages of modularityand distributed control made possible by the disclosed refrigerationsystem are not lost.

BCMCC 744 and the third party controls 746 and 748 may be collectivelyreferred to as remote terminals associated with third field bus controlnetwork 740. In one construction, the communication bus 741 comprises awireless RF interface (also referred to as an RF link) such that nowiring is required between the remote terminals and the interfacegateway 714. Using a wireless RF interface provides substantialadvantages, including reducing the amount and complexity of field wiringneeded to install the system, and greatly reducing the risk of damagedue to external influences such as lightening strikes, high voltagearcing, or high current transmissions in adjoining equipment/wiring.Such external influences are common in some geographic regions and canresult in considerable system downtime and/or service expense. RFinterfaces may be implemented using broad band spread spectrum (BBSS)transmission systems or narrow band on/off keyed (OOK) transmissionsystems. BBSS systems provide improved data integrity performance withrespect to data transmitted in harsh electrical environments, and oftenprovide higher data throughput rates. OOK systems, on the other hand,are typically less expensive to implement. It should be understood,however, that the third field bus control network 740 may be completely“hard wired” or partially wireless and partially hard wired.

A remote, wireless interface device 750 can be used by system operators,maintenance personnel, and the like to communicate directly with one ormore case controllers such as BCMCC 744. In one construction, theinterface device 750 comprises an infrared transceiver that operates asa remote keypad for a display module associated with the casecontroller. Thus, interface device 750 can be used to query casecontrollers to determine information such as current temperature or setpoint information or, optionally, to input set point data into casecontrollers. Such set point data can include, among other items, defrostschedules or temperature set point data. In the construction illustratedin FIG. 7, however, BCMCC 744 receives its primary control inputs fromrack PLC 720.

In addition to the three field bus networks already described withrespect to FIG. 7, the distributed intelligence control system 700 alsoincludes local and remote human-machine interface (HMI) devices. Aremote HMI device 752 provides user access to system status information,which is transmitted to the remote HMI device via network 731. In oneconstruction, the remote HMI device 752 comprises a touch screen device,such as a TP 170A device, available from Siemens (part no.6AV6545-0BA15-2AX0). Similarly, a local HMI device 754 provides useraccess to system configuration data, system status data, diagnosticdata, and the like. The local HMI device 754 communicates with rack PLC720, via network 731. In the construction illustrated in FIG. 7, thelocal HMI device 754 comprises an LCD display with a membrane keyboard,such as an OP3 device, which is available from Siemens (part no.6AV3503-1DB10). Additional details regarding constructions of remote HMIdevice 752 and local HMI device 754 are provided in the Appendix.

One of the advantages of using a distributed intelligence controlsystem, such as the system of FIG. 7, is that such a system is generallyeasier to install than conventional systems, which typically requiremultiple runs of high power wiring between the rack and each remotelylocated controlled device, such as display cases, as well as separatewiring to/from each system sensor. For example, prior art systemstypically require at least one additional separate wire, often a highpower wire requiring compliance with particular standards, for eachsystem element being controlled.

In addition, the distributed intelligence control system is, in oneconstruction, at least partially self-configuring. For example, eachAS-i bus compatible device can generate its own unique identification(ID)/address. An AS-i master queries each device on the system, and thatdevice tells the AS-i master its ID/address. For one example method ofoperation, each BCCSCM on control network 716 would indicate to rack PLC720 that it is a compressor control module as well as its ID/address. Inthe event that a duplicate ID/address is generated, the AS-i masterinstructs the device to pick another value. Thus, as can now beappreciated, a complicated refrigeration control system can be installedwith a reduced complexity in the installation process because personsinstalling the system need not concern themselves with all of thedetails associated with identifying and addressing each control modulein the system.

Likewise and in another construction, each distributed control module insystem 700 (e.g., BCCSCM 48, BCSBM 724, BCVCM 726, BCFCM 736, and BCMCC744) includes processing capability, data storage capability, andprovides configuration/set point mirroring, whereby the most recentsystem configuration and set point data for each module is stored inthat module. Such configuration and set point data includes, forexample, module ID/address information, control system set points (e.g.,case temperature), defrost cycles, alarm history, and the like. Thus, ifrack PLC 720 fails and needs to be reprogrammed or replaced, the entiresystem partially reconfigures itself and supplies the most recentconfiguration and set point data to the new/repaired rack PLC.Similarly, if communication with rack PLC 720 is lost, each controlmodule in system 70 can continue to attempt to maintain control byadhering to the most recent set points/schedules provided by rack PLC720. In this way, the integrity and history associated with system 700is maintained even when rack PLC 720 is replaced.

More detailed methods of operation for configuring a refrigerationsystem 700 will now be described in connection with FIGS. 7 and 17–22.When manufacturing or assembling a device or subsystem (e.g., anevaporator, a compressor, a condenser, a refrigeration case, a systembranch, etc.) the device manufacturer or assembler (collectivelyreferred to below as manufacturer) couples the device or subsystemcontroller (e.g., the BCVCM(s) 726, BCSBM(s) 724, BCCSCM(s) 48 and/or1500, BCFCM(s) 736, BCMCC 744, condenser PLC 732) to the related deviceor subsystem. In addition, the device manufacture stores anidentification code (e.g., model number, serial number, device type,etc.) for the device or subsystem (collectively referred to below asdevice) in the related device controller. As discussed in connectionwith FIG. 7, the device controllers are connected (either directly orindirectly) with the rack PLC 720 (which is also referred to as thesystem controller). Before proceeding further, it should be noted thatthe rack PLC may also be referred to as the system controller 720.However, unless specifically limited otherwise, other processing unitscan be used in place of or in combination with the rack PLC to performone or more operations disclosed below.

With reference to FIG. 7, the one or more technicians assemble thephysical structure of the refrigeration system. After or concurrent withassembling the physical structure, the one or more technicians activatethe rack PLC 720 and the computer 714. Among other initial operationsperformed by the rack PLC 720 and the computer 714, the rack PLC 720establishes a communication network with the devices of therefrigeration system and determines what devices are included with therefrigeration system. In general, the rack PLC 720 initiates one or moresignals requesting the device controllers to identify themselves, andidentify what devices are coupled to the device controllers (e.g., viathe identification codes). Further, the rack PLC 720, with the help ofthe communication modules (e.g., the gateway interface 714, AS-i masters722, 734, etc.), establishes the protocols and addresses forcommunication in the refrigeration system.

After establishing the communication network and the elements of therefrigeration system, the rack PLC 720, with the assistance of the PCinterface 714, configures the refrigeration system by providinginformation (e.g., control and safety parameters, schedules, signals,etc.) to the device controllers. For example, the rack PLC 720 and/orthe PC interface 714 includes in memory the identification codes forvarious devices that can be attached to the refrigeration system. As aspecific example, hundreds of compressor models can be used in therefrigeration system and, consequently, the rack PLC 720 and/or the PCinterface includes in memory an identification code (e.g., model number)for each possible compressor. Associated with each identification codein memory are limits, equations, values, and other information used bythe refrigeration system for operation. Further, databases may also beused for obtaining information based on combination of identificationcodes. Using the identification codes, the rack PLC acquire values,parameters (control and safety parameters), equations, limits, etc. frommemory; perform calculations using the acquired information (e.g.,calculate values or limits for the one or more parameters, createschedules, etc.); and acquire similar information from other processingunits. The information received at the device controllers is used by thedevice controllers to locally operate (or control) the devices.

The device controllers (e.g., the BCCSCM described earlier) can includeone or more sensors that sense parameters identified by the rack PLC720. The sensed values are communicated via the establishedcommunication network to the rack PLC 720. The rack PLC uses the sensedparameters, stored information/data regarding the refrigeration system,and information stored at the rack PLC (or at other processing unitssuch as the PC interface 714) to operate (or control) the refrigerationsystem. Controlling the refrigeration system includes providing controlsignals and information to the device controllers for operating thedevices.

Referring now to Tables 1–4, the tables disclose what parameters aremaintained at each module for one construction of the refrigerationsystem. Table 1 discloses the parameters maintained at the compressorcontrol module.

Compressor Module (BCCSCM) Configuration Data Operating Parameter SourceCompressor Model Number Manufacture (User Input) Suction Pressure Cut-inSystem Controller Suction Pressure Cut-Out System Controller SplitSuction Assignment System Controller Discharge Pressure High LimitSystem Controller Discharge Temperature High Limit System ControllerMotor Current Limit System Controller AS-i Address Manufacture (UserInput) Compressor Type System Controller Number of Sensors InternalDetermination Operating Voltage System Controller Oil Pressure LimitSystem Controller Oil Level Switch Enabled Internal Determination MotorTemp Limit System Controller

With reference to Table 1, the manufacturer of each compressor enters acompressor model number into the compressor control module. Thecompressor model number, when retrieved by the rack PLC 720, identifiesthe respective compressor. Using the compressor model number, the rackPLC 720 can obtain related data for the compressor. For example, basedon the compressor model number, the rack PLC 720 can obtain thespecifications for the compressor, such as compressor manufacture,compressor type (e.g., scroll, screw, reciprocating, etc.), capacity,safety limits, etc. Also, as discussed above, the rack PLC 720communicates one or more operating parameters to the compressor controlmodule. The parameters provided from the rack PLC 720 to the compressorcontrol module are identified in column two of Table 1 as “SystemController.” Other parameters may be communicated from the systemcontroller to the control module and not all parameters are required forthe control module in all constructions.

Referring again to Table 1, some of the parameters are established orcalculated by the compressor control module. For example, the “number ofsensors” parameter is an internal calculation performed by thecompressor control module. For example and in one construction, thecompressor control module polls for sensors connected to the module.Based on the response, the compressor module can determine how manysensors are connected to the module.

The oil level switch enabled parameter is also an internal determinationfor the construction shown in Table 1. For some compressor types (e.g.,scroll compressors), an oil level switch is used to control the oillevel of the compressor. The compressor module performs an internaldetermination whether an oil level switch is attached and enabled.

Referring again to Table 1, the parameter “AS-i Address” is identifiedas a manufacturer or user input. The AS-i address parameter is used bythe network for promoting communication between the system controllerand the respective compressor module. The system controller cansubsequently modify the AS-i address parameter to allow for automaticaddressing of the attached device.

Table 2, System Module (BCSBM) Configuration Data, discloses theparameters maintained at the system branch control module for oneconstruction of the refrigeration system.

System Branch Module (BCSBM) Configuration Data Operating ParameterSource Case Model Number Manufacture (User Input) Defrost ScheduleSystem Controller Discharge Air Temp Set Point System Controller DefrostType System Controller Number of Defrosts per Day System ControllerDischarge Air Temperature High Limit System Controller DefrostTermination Temperature System Controller AS-i Address Manufacture (UserInput) Time and Date System Controller

Similar to what was discussed above for the compressor control module,the manufacture of each system branch control module enters a case modelnumber into the control module. The case module number identifies therespective case model to the rack PLC 720. Using the case model number,the rack PLC 720 obtains information relating to the case and the systembranch. Also, as discussed earlier, the rack PLC 720 communicates one ormore operating parameters to the system branch control module. Theparameters provided from the rack PLC 720 to the system branch controlmodule are identified in column two of Table 2 as “System Controller.”This information can be maintained at the system controller and at theindividual modules. Other parameters may be communicated from the rackPLC 720 to the system branch control module and not all parameters arerequired for the system branch control module in all constructions. Itis also envisioned that the identifying model number can be assigned byinstallation or service personnel via the system controller for fieldreplacement of a failed device.

Referring again to Table 2, the parameter “AS-i Address” is identifiedas a manufacturer or user input. The AS-i address parameter is used bythe network for promoting communication between the system controllerand the respective system branch control module. The system controllercan subsequently modify the AS-i address parameter to allow forautomatic addressing of the attached device.

Table 3, Valve Module (BCVCM) Configuration Data, discloses theparameters maintained at the valve control module for one constructionof the refrigeration system.

Valve Module (BCVCM) Configuration Data Operating Parameter Source ValveModel Number/Application Code Manufacture (User Input) Number of StepsInternal Determination Failsafe Position System Controller AS-i AddressManufacture (User Input)

The manufacture of each valve enters a valve model number/applicationcode into the valve control module. The valve model number identifiesthe respective valve attached to the valve control module. Using thevalve model number, the system controller can obtain informationrelating to the valve. The parameter(s) provided from the systemcontroller to the valve control module includes the failsafe positionparameter for the valve. This parameter can be maintained at the systemcontroller and at the individual modules. Other parameters may becommunicated from the rack PLC 720 to the valve control module and notall parameters are required for the valve control module in allconstructions.

Referring again to Table 3, the parameter “AS-i Address” is identifiedas a manufacturer or user input. The AS-i address parameter is used bythe network for promoting communication between the system controllerand the respective system branch control module. The system controllercan subsequently modify the AS-i address parameter to allow forautomatic addressing of the attached device.

Additionally, the “number of steps” parameter is a parameter establishedby the valve control module. For example, the “number of steps”parameter is an internal calculation performed by operating a steppermotor attached to the valve and determining the number of stepsperformed by the stepper motor.

Table 4, Case Control Module (BCMCC) Configuration Data, discloses theparameters maintained at the system branch control module for oneconstruction of the refrigeration system.

Case Control Module (BCMCC) Configuration Data Operating ParameterSource Case Model Number Manufacture (User Input) Defrost ScheduleSystem Controller Discharge Air Temp Set Point System Controller DefrostType System Controller Number of Defrosts per Day System ControllerDischarge Air Temperature High Limit System Controller DefrostTermination Temp System Controller Network Address Manufacture (UserInput) Number of Sensors Internal Determination EEPR Attached Y/NInternal Determination Number of Steps Internal Determination FailsafeEEPR Position System Controller Time and Date System Controller

The manufacture of each case enters a case model number into therespective BCMCC. The case module number identifies the case modelattached to the case control module. Using the case model number, therack PLC 720 can obtain information relating to the case. For example,based on the case module number, the system controller can obtain thespecifications for the case. The rack PLC 720 communicates one or moreoperating parameters to the case control module. Additionally, the rackPLC 720 can create and provide one or more schedules to the case controlmodule. The parameters provided from the rack PLC 720 to the casecontrol module are identified in column two as “System Controller.”Other parameters may be communicated from the rack PLC 720 to the casecontrol module and not all parameters are required for the case controlmodule in all constructions.

Referring again to Table 4, some of the parameters are established orcalculated by the case control module. For example, the “number ofsensors” parameter is an internal calculation performed by the casecontrol module. For example and in one construction, the case controlmodule polls for sensors connected to the module. Based on the response,the case control module can determine how many sensors are connected tothe module. Other parameters determined internally at the control moduleinclude the parameters: “EEPR attached Y/N” and “number of steps.” Forthe “EEPR Attached Y/N” parameter, the case control module polls whetheran EEPR is attached to the case control module. The “number of steps”parameter is an internal calculation to determine the number of steps anattached stepper motor includes. This calculation is performed if thecase includes an EEPR.

Referring again to Table 4, the parameter “Network Address” isidentified as a manufacturer or user input. It should be noted that, forthe construction shown in FIG. 7, the case control module communicateswith the system controller, via the PC interface, on a RS-485 networkusing a modbus protocol. Therefore the network address is not an AS-iaddress.

With reference to FIG. 7, the fan control module (BCFCM) is a controllerthat activates/deactivates an attached fan. A table of the parametersfor the fan control module is not provided because, for the constructionshown, the BCFCM only activates or deactivates the fan. However, therack PLC 720 communicates with the fan control module via the condenserslave module and AS-i master as shown in FIG. 7 and as described above.Therefore, address information is still communicated with the rack PLC720 based on the principals described herein

FIGS. 17–21 include five tables that represent the informationcommunicated to and from the rack PLC 720. The table 1700 (FIG. 17)includes parameters associated with rack data. The table 1800 (FIG. 18)includes parameters associated with suction group data. The table 1900(FIG. 19) includes parameters associated with compressor data. Theparameters in table 1900 are repeated for each compressor of therefrigeration system. The table 2000 (FIG. 20) includes parametersassociated with system data. The parameters in table 2000 are repeatedfor each system branch of the refrigeration system. The table in FIG.2100 (FIG. 21) includes parameters associated with condenser data.

As discussed earlier, before the refrigeration system (e.g., system 700)can operate, the network needs to map (or identify) the components ofthe system before the components can communicate among themselves. Thatis, the addressing system for the components of the network needs to bein place before communication among the network can occur. The rack PLC720 and/or the PC interface 714 initiate call signals or requests todetermine what elements make up the communication network.

For example, the rack PLC 720 commands the attached AS-i master 722 toscan what is attached to the AS-i master 722. In response to callsignals initiated by the AS-i master, each compressor control module 48(or 1500), system branch module 724, and valve module 726 responds bycommunicating respective addresses to the AS-i master. Based on theresult, the AS-i master 722 informs the rack PLC 720 how many modulesare attached to the AS-i master 722 and provides addresses to the rackPLC 720 allowing the rack PLC 720 to communicate with the controlmodules via the AS-i master 722. Similarly, the rack PLC 720 and/or PCinterface 714 obtains addressing information from the condenser slavecontroller 732, and third party controls 724 and 748. Additionally, therack PLC 720 and/or PC interface 714 can obtain addressing informationfrom the local HMI 754, remote HMI 752, wireless hub 713, localworkstation 704, local network server 702, remote workstation 706, etc.The rack PLC 720 can then build a map of the refrigeration system 700 asa result of this information.

Once the communications network is established, the rack PLC 720 beginsdeveloping refrigeration system 700. In general, parameter informationis communicated among components of the system, resulting in the rackPLC 720 configuring the system. The rack PLC 720 requests a module toidentify the component (e.g., compressor, case, valve, condenser)attached to the module. For example, each component can provide a modelor ID number identify the respective component. In response to receivingthe information, the rack PLC 720 obtains information stored frommemory. The information includes safety information, which isselectively shared with the appropriate module(s). The information alsoincludes operation information (control parameters, schedules, etc.),which is also selectively communicated to the appropriate module(s).Further discussion about what how information is obtained, whereinformation is communicated, and where information is stored isdiscussed in connection with FIG. 17–21.

With reference to tables 1700, 1800, 1900, 2000, and 2100, the firstcolumn in each table 1700–2100 relates the parameters associated witheach data group. The second column of each tables 1700–2100 indicatesthe original source of the related parameter. The different types oforiginal sources include an operator entering the data for theassociated parameter (referred to as “operator input”), a network queryfrom the system controller to a networked device (referred to as“network query”), a parameter received from a control module (referredto as “BCVCM,” “BCSBM,” “BCCSCM,” “BCMCC,” or “BCFCM”), a parametercalculated using one or more pieces of information already obtained(referred to as “calculated”), and a parameter obtained from memory(referred to as “case database” or a variation thereof). For example,the “rack name” parameter of the rack data table 1700 identifies theoperator as providing the necessary information. The “number of systems(n)” parameter of the rack data table 1700 is obtained by the rack PLC720 performing a network query to determine the number of branch systemsattached to the rack PLC 720. The “main liquid valve type” parameter ofthe rack data table 1700 is obtained from the valve control module 726.The “suction pressure set point” parameter of the suction group datatable 1800 is a calculated parameter based on refrigerant type and casedischarge air set point. Equations known to one skilled in the art canbe used to calculate the suction pressure set point. The “operatingcurrent data” parameter of the compressor data table 1900 is obtainedfrom a database stored at the PC interface 714. Other parameters withinthe tables 1700–2100 are obtained using similar methods.

The data and/or information for each parameter is obtained sequentiallyand is obtained in approximately the order as shown in FIGS. 17–21.However, as also discussed, the order of obtaining the information canvary. Regardless of the order, tables 1700–2100 identify the parameterscommunicated to and from the rack PLC 720 for one configuration of therefrigeration system 700.

The third and fourth columns 1700–2100 identify whether the parameter ismanually entered or automatically obtained.

The fifth column identifies where each parameter is stored, andidentifies from where the parameter is initiated and to where theparameter is communicated. As used within tables 1700–2100, the symbol“C” identifies the parameter being stored at the PC interface 714. Thesymbol “P” identifies the parameter being stored at the rack PLC 720.The symbol “M” identifies the letter being stored at a device controlmodule. The symbol “AM” identifies the parameter being stored at theAS-i master 722. The symbols “>” and “<” identify the flow of thecommunication (i.e., “source>destination” and from“destination<source”).

For example, the “rack name” parameter of table 1700 is maintained atboth the PC interface 714 and the rack PLC 720. Additionally, the rackname is originally entered at either the PC interface 714 or the systemcontroller 720, and is subsequently communicated to the other processingunits.

For another example, the “compressor model number” parameter originatesat the compressor control module 48 (or 1500) and is communicated to therack PLC 720. From the rack PLC, the compressor model number iscommunicated from the rack PLC 720 to the PC interface 714.

For yet another example, the “number of systems (n) parameter” parameteris obtained during a network query, and is communicated from the AS-imaster 722 to either the PC interface 714 or the rack PLC 720 and thenis shared to both the PC interface 714 and the rack PLC 720. Otherparameters of tables 1700–2100 are communicated similarly. Beforeproceeding further, it should be noted that the tables 1700–2100 presentone construction for the refrigeration system. The parameters used, thesource of the parameters, how the information is obtained for eachparameter, the storage location for each parameter, and how a parameteris calculated (if necessary) can vary for other constructions. Moreover,it is envisioned that not all of the parameter shown in tables 1700–2100may be used and other parameters can be added. Also and as discussedearlier, while the rack PLC 720 and PC interface 714 are shown asseparate components, it is envisioned that these components and/orfunctions performed by these components can be combined or divideddifferently. Therefore, other constructions of the refrigeration systemcan affect the tables 1700–2100.

The last column of each table 1700–2100 identifies the parametersnecessary for calculating a value or limit.

Once the refrigeration system 700 is configured, the system can beginoperation. Of course, one or more subsystems can begin operation (beforeoperation of the refrigeration system as a whole) as the necessaryinformation for operating the subsystem(s) is obtained at thesubsystem(s). Once operation of the refrigeration system 700 begins, thesystem can perform a subsequent configuration. Reasons for a subsequentconfiguration include an alarm resulting in the deactivation of a deviceor subsystem, the operator changing the refrigeration system (e.g.,adding a component such as adding a compressor), and the refrigerationperforming a periodic update or review.

For example, if a compressor 14 is added or removed from the system 700,the operator can inform the rack PLC (e.g., via the PC interface 714) toperform a new configuration for the whole system. Alternatively, theoperator can have the system controller update the existingconfiguration in view of the added component. As another example, thesystem can perform all of or a portion of the configuration process aspart of a periodic maintenance program.

As yet another example, the system can perform all of or a portion ofthe configuration process when an alarm is detected at the componentlevel. For example, the device controllers receive the safety parametersfor the device. When a sensed value of a safety parameter is outside ofa sensed limit, the device controller generates an alarm and deactivatesthe device. The alarm, the parameter causing the alarm, the value of theparameter, and the time and date of the alarm is communicated to therack PLC. Upon receiving the alarm, the rack PLC 720 can perform all ora portion of the configuration process to update the system in view ofthe alarm. For example, if a compressor control module 48 (or 1500)detects an alarm condition, the rack PLC 720 can reconfigure the runpattern of the compressors 14 (discussed earlier) in view of thedeactivation of the faulty compressor. Other aspects of therefrigeration system can be reconfigured when an alarm is generated by adevice. That is, depending on the location of the error, the rack PLC720 will reconfigure the appropriate operation for the component,related components, and/or related subsystems (generally referred to asapplicable components), which relate to the alarm.

In another example, when a component does fail and require replacement,the replacement of the component may result in a new or different devicecontroller being added to the system. The system controller identifiesthat a device controller has been removed and identifies a newcontroller has been installed. The new device controller may be the sametype as the replaced controller. If the new component/controller is thesame as the replaced component/controller, then the new devicecontroller can be configured the same as the old controller. If thenew/component controller is different than the replaced/componentcontroller, then the system controller can reconfigure the portion ofthe refrigeration system including the new device controller.Additionally, the system controller can modify the control parameters ofother modules/components to preempt a trending condition that couldcause alarm in a single offending module.

Before proceeding further, it is envisioned that in one construction ofthe refrigeration system, the rack PLC 720 can detect the likelihood ofan alarm not yet detected at the component level using data acquiredfrom multiple systems. More specifically, the rack PLC 720 obtainsacquired data from multiple devices. Based on acquired data from a firstdevice, the rack PLC 720 can speculate eventual damage to a seconddevice. The rack PLC 720 can generate an alarm condition resulting inthe deactivation of the first and/or second device, reconfigure therefrigeration system, and communicate the alarm to the high-leveldevices.

It should also be noted that while operations of the system aredescribed above, the order of operation could vary. That is, therefrigeration system is a complex system having many parameters (orvariables), components, subsystems, etc. Because of the flexibility ofthe distributed system, a skilled artisan in the field of refrigerationcan vary when various operations discussed herein are performed.Therefore, the invention is not limited to the order of operationsdiscussed herein.

FIG. 8 is a block diagram of aspects of the integrated distributedintelligence control system of FIG. 7. FIG. 8 illustrates the use ofwireless interfaces between the first field bus control network 716, thesecond field bus control network 730, and the third field bus controlnetwork 740. Further, FIG. 8 illustrates locating one or more casecontrollers (e.g., BCMCC 802) remote from communication bus 741.Finally, FIG. 8 also illustrates locating additional valve controllers(e.g., BCVCM 804, 806) on communication bus 741 and remotely.

In the partially wireless system depicted in FIG. 8, an MPI compatibleRF interface is used to facilitate communications between rack PLC 720and condenser PLC 732, and between rack PLC 720 and remote HMI 752. Moreparticularly, rack PLC 720 communicates via a wire-based MPI interface731 with a first MPI compatible RF transceiver 810. It is believed thatDECT compliant devices (e.g., DECT Engine MD 32), available fromSiemens, can be used to facilitate an MPI compatible wireless interface.A second MPI compatible RF transceiver 812 is associated with condenserPLC 732. Similarly, a third MPI compatible RF transceiver 814 isassociated with remote HMI 752.

As explained above with regard to FIG. 7, it is preferable in someconstructions to use a LonWorks® compatible bus system for the thirdfield bus network 740. This is because such compatibility is believed tofacilitate connectivity and interoperability with third party controls746 and 748. Further, such a bus typically enjoys a range (i.e., thereliable length of the bus) that exceeds the recommended range of theAS-i standard. Accordingly, in the construction illustrated in FIG. 8,LonWorks® compatible RF interfaces 818, 820, and 822 are used forcommunications between rack PLC 720, remote case controller 802 (BCMCC802) and remote valve controller 806 (BCVCM 806). More particularly, theRF interfaces 818, 820, and 822 comprise narrow band RF transceivers,such as RF to Twisted Pair Routers for LonWorks® (also referred to as anRF/TP-49 Router).

As can now be appreciated from the constructions illustrated in FIGS. 7and 8, rack PLC 720 operates as a master device and communicates withvarious slave control devices via a plurality of network interfaces. Forexample, rack PLC 720 communicates with local device-level controllers(BCSBM 724, BCCSCM 48 (or 1500), and BCVCM 726) via local AS-i bus 728.Rack PLC 720 communicates with condenser PLC 732 to control fancontroller (BCFCM 736) and fan(s) 830 via an MPI compatible RF interfacecomprising a hard wired MPI interface 731 between rack PLC 720, local RFinterface 810, and remote RF interface 812. Rack PLC 720 communicateswith case controllers BCMCC 744 and 802 via communication bus 741, and awireless link established between RF interfaces 818 and 820. Likewise,rack PLC 720 communicates with valve controllers BCVCM 804 and 806 viacommunication bus 741, and a wireless link established between RFinterfaces 818 and 822.

FIG. 9 is a block diagram of a bus compatible refrigeration branchcontrol system 900, suitable for use as part of a refrigeration system,including the systems depicted in FIGS. 7 and 8. A refrigeration branchincludes a number of refrigeration units (e.g., display cases, coldstorage rooms, and the like) sharing a common closed-loop refrigerationcontrol path. As illustrated construction of FIG. 9, the refrigerationbranch control system 900 includes a Bus Compatible System Branch ModuleBCSBM 724, which is constructed and arranged for communication with rackPLC 720 via field bus control network 728 (e.g., a local AS-i bus). Itshould be understood that multiple BCSBMs could be employed in arefrigeration system having multiple refrigeration branches. Forconvenience, the operation of one construction of a bus compatiblerefrigeration branch control system (e.g., system 900) will be describedwith respect to a system having only a single refrigeration branch. Itis also to be understood that the disclosure herein may be scaled toaccommodate systems employing multiple refrigeration branches. TheAppendix hereto identifies one hardware configuration for a BCSBM.Briefly stated, for the construction shown, the BCSBM comprises aprocessing capability and a data storage capability.

BCSBM 724 effects branch control by controlling the operation of aplurality of solid-state relay devices (SSRs). Such SSRs may include,for example, a suction stop SSR 902, a liquid line SSR 904, and a gasdefrost SSR 906. In the construction illustrated in FIG. 9, BCSBM 724individually controls each of the SSRs 902, 904, and 906. For example,BCSBM 724 controls the suction stop SSR 902 via a first defrost controlsignal 910. Similarly, BCSBM 724 controls the liquid line SSR 904 via atemperature/refrigeration control signal 912. BCSBM 724 also controlsthe defrost SSR 906 via a second defrost control signal 914. In oneconstruction, each of these control signals 910, 912, and 914 comprisesan on/off signal, directing the associated SSR to be either opencircuited (non-conducting) or close circuited (conducting). It should beunderstood that each of the SSRs 902, 904, and 906 is connected to anassociated control valve (valves not shown) such that when thecorresponding control signal 910, 912, or 914 is asserted, the SSRconducts and the associated control valve is opened or closed, asappropriate. Finally, BCSBM 724 controls an electronic evaporatorpressure regulator valve (EEPR valve) 920 associated with therefrigeration branch via a control line 922. Of course, other devicescan be used in place of the SSRs.

Advantageously, the BCSBM 724 provides for distributed control ofrefrigeration and defrost cycles of an associated refrigeration branch.For example, in one construction, temperature control for a branch isachieved by positioning the associated EEPR valve 920. Case/fixturetemperature(s) (e.g., discharge air temperature) is/are provided to rackPLC 720 by a bus compatible modular case control subsystem (e.g., BCMCC744, which is described in greater detail below with respect to FIGS.11–13). As such, the system does not require wiring a separate,additional temperature sensor for branch control because existingtemperature data is made available to BCSBM 724 via BCMCC 744 and rackPLC 720. Based on the provided temperature information, rack PLC 720transmits the desired set point to BCSBM 724 over local field busnetwork 728. BCSBM 724 then drives EEPR valve 920 to the desired settingvia control line 922. In another construction, case temperature, dooropen/close, and defrost termination inputs are added to the BCSBM 724.This allows for operation of branch systems without the need of feedbackfrom the BCMCC.

BCSBM 724 can also affect a degree of temperature control by cycling theliquid line solenoid via the liquid line SSR 904. In this regard, rackPLC 720, in one construction, receives discharge air temperaturereadings from one or more display cases being cooled by therefrigeration branch. Such temperature information originates from oneor more bus compatible modular case controllers, as described below.Based on the received temperature information, rack PLC 720 providesliquid line commands to BCSBM 724 over local field bus network 728.BCSBM 724 thereafter cycles liquid line SSR 906 viatemperature/refrigeration control line 912.

In another construction, case temperature, door open/close, and defrosttermination inputs are added to the BCSBM 724. This allows for operationof branch systems without the need of feedback from the BCMCC.

Referring still to FIG. 9, BCSBM 724 can also be used for defrosting anevaporator coil associated with the refrigeration branch. For example,in one construction, rack PLC 720 determines the defrost scheduling foreach branch. When a particular branch is scheduled to commence a defrostcycle, rack PLC 720 instructs BCSBM 724 to begin the defrost cycle.BCSBM 724 thereafter drives the first defrost control line 910 to causethe suction stop SSR 902 to operate the suction stop solenoid so as tocut off the refrigeration cycle. At or about the same time, BCSBM 724also drives the second defrost control line 914 to cause the gas defrostSSR 906 to open a gas defrost solenoid that allows a gas (e.g., hot gas)to flow through the evaporator coil and through a check valve associatedwith the liquid line solenoid—in effect, operating the system inreverse. It is to be understood that the use of a hot gas defrost cyclereflects an exemplary construction only; the system can be employed withcool gas defrosting, electric defrosting, and other known methods ofdefrosting. When the defrost cycle is complete (which may be determinedon the basis of time or temperature or other criteria), rack PLC 720sends an appropriate message to BCSBM 724 to terminate the defrost cycleand begin a new refrigeration cycle.

At the end of a defrost cycle, it may be desirable to initiate a dripcycle in which condensate on the coil is allowed to drip off and flowout through a drain. If a drip cycle desired, rack PLC 720 sends anappropriate command to BCSBM 724 at the end of the defrost cycle. Ratherthan start a new refrigeration cycle, however, BCSBM 724 removes thesecond defrost control signal 914 thereby causing the gas defrost SSR902 to open the gas defrost solenoid, while BCSBM 724 continues to applythe first defrost control signal 910 and maintain the suction stopsolenoid in the closed position, via suction stop SSR 902. Thiscontinues until the drip cycle terminates.

Similarly, when a fixture/case associated with the refrigeration branchis being cleaned or subject to a maintenance action, it is not normallydesirable to operate a refrigeration cycle. Therefore, in such a mode,rack PLC 720 sends a command to BCSBM 724, which causes suction stop SSR902 to close the suction stop solenoid.

Referring still to FIG. 9, modular branch control system 900 provides,in one construction, a degree of back-up capability, thereby improvingoverall system robustness, should one or more components fail. Forexample, if communication with rack PLC 720 is lost, BCSBM 724 isconstructed and configured so that it maintains the recent refrigerationand defrost set point and cycle information. Thus, the refrigerationbranch remains operable despite the loss of communications with rack PLC720. Also, when multiple branch control modules are employed to controlmultiple refrigeration branches, it is preferable that only one branchbe in a defrost cycle at any given time. Normally, this scheduling iscoordinated by rack PLC 720. In the event that communications with rackPLC 720 are lost, however, each branch controller preferably continue tooperate on its prior schedule so that the defrost cycles continue to runat non-overlapping times, despite the loss of communications with rackPLC 720.

Similarly, if the temperature associated with one or more display casesin the branch is being controlled by a local case controller (e.g., aBCMCC as illustrated in FIG. 11) and that local case controller fails,BCSBM 724 can maintain a degree of temperature control by cycling liquidline SSR 904, in a manner similar to that described above.

FIG. 10 is a block diagram of a commercial refrigeration system that iscompatible with the systems depicted in FIGS. 7 and 8, includingmultiple bus compatible valve controllers. The commercial refrigerationsystem illustrated in FIG. 10 includes one or more Bus Compatible ValveControl Modules (BCVCMs) 726, 804, and 806.

Each of the BCVCMs 726, 804, and 806 is constructed and arranged, in oneconfiguration, to control an electronically controlled valve associatedwith the commercial refrigeration system. For a more specificconstruction, each BCVCM is constructed to receive at least one valveposition signal and provide at least one valve drive signal. In oneconstruction, each BCVCM provides a stepper drive output for driving astepper-motor controlled valve. It is to be understood, however, thatthe system can be modified for use with other types of valves, such assolenoid controlled valves. A non-exhaustive list of the types ofrefrigeration system valves that may be controlled in accordance withthe distributed intelligence control system include, for example, heatreclaim valves, electronic evaporator pressure regulator valves (e.g.,EEPR valves using a stepper-motor rather than a solenoid valve),flooding valves, main liquid pressure reduction valves, receiverpressure regulator valves, surge receiver control valves, splitcondenser valves, defrost control valves, secondary cooling controlvalves, oil control and separation valves, and electronic expansionvalves (e.g., in a display fixture or a subcooler). Other examples ofsystems and valves adapted to be controlled by the system may be foundin U.S. Pat. Nos. 3,343,375, 4,478,050, 4,503,685, 4,506,523, 5,440,894,5,743,102, 5,921,092, and 6,067,482, each of which is incorporatedherein by reference. The Appendix hereto identifies one hardwareconfiguration for a BCVCM.

The first BCVCM 726 will be used here as an example. As illustrated inFIG. 10, BCVCM 726 is configured to control an electronic expansionvalve associated with a subcooler in a low temperature refrigerationbranch. Those skilled in the art will recognize that subcoolers may beused to improve system efficiency by helping to shift some of the totalsystem load from low temperature branches to medium or high temperaturecompressors. First BCVCM 726 communicates directly with rack PLC 720 viafield bus control network 728 (e.g., a local AS-i bus) to control theoperation of a first electronically controlled valve 1002. The firstBCVCM 726 determines the position of the first electronically controlledvalve 1002. This step is illustrated schematically as a line 1004 (seealso lines 1014 and 1024). In one construction, no physical valveposition feedback lines are required. Rather, each electronicallycontrolled valve (e.g., valve 1002) is a stepper-motor controlled valve.The associated BCVCM determines valve position by keeping track of thenumber of steps the stepper motor has moved relative to a knownreference point (i.e., zero point). In order to maintain control, theBCVCM periodically calibrates the valve position by temporarilyreturning to the reference point and moves the valve to the lastcommanded position (step) relative to the reference point. With thecurrent position of the valve known, first BCVCM 726 provides the valveposition information to rack PLC 720 via control network 728. Similarly,rack PLC 720 provides a desired valve position signal to first BCVCM 726via control network 728. Upon receipt of the desired positioninformation, first BCVCM 726 provides a valve drive signal to the firstelectronically controlled valve 1002, via line 1006, to position thevalve in the desired position.

The operation and control of the second BCVCM 804, a second valve 1012,and lines 1014 and 1016 is substantially similar to the operation of thefirst BCVCM 726. The second BCVCM 804 illustrated in FIG. 10, however,is not located on field bus control network 728. Rather, BCVCM 804 islocated at a position sufficiently remote from rack PLC 720 to require adifferent bus, such as field control bus 741 (e.g., a LonWorks®/Echelonbus). Likewise, the third BCVCM 806 operates substantially similarly tothe first and second BCVCMs 726 and 804, except that BCVCM 806communicates with rack PLC 720 via a wireless RF interface (as alsoillustrated in FIG. 8).

As can now be appreciated, employing valve controllers such as BCVCMs726, 804, and 806 facilitates distributed control of the totalrefrigeration system and minimizes the amount of high power wiringrequired to provide integrated control of a plurality of system valves.

It should be understood that while FIG. 10 illustrates a system havingthree BCVCMs—BCVCM 726 located on a local AS-i bus, BCVCM 804 located onbus having a relatively longer distance capability (e.g., control bus741), and BCVCM 806 located on an RF compatible bus—the system is notlimited to such an arrangement. Rather, a BCVCM may be used with eachmotor-driven valve requiring independent monitoring and control.Examples of such motor driven valves are provided in the Appendix.

FIG. 10A is an exemplary schematic of a construction related topeer-to-peer control/communication. More particularly, FIG. 10Aillustrates peer-to-peer communications between a case controllerconfigured as a fixture/display monitor (e.g., BCMCC 744; see also FIGS.11–13) and a valve controller configured to control an evaporator valveassociated with a subcooler on a low temperature refrigeration branch. Aliquid temperature probe (e.g., digital case sensor 1102) is installedat the inlet to each expansion valve or, alternatively, at the liquidline inlet to each case/fixture lineup (not shown). The liquid lineprobe provides digital temperature data to the case controller (BCMCC744), which provides the temperature data to rack PLC 720. Rack PLC 720supplies an evaporator valve control command to the valve controller(BCVCM 726) which causes the valve controller to drive valve 1002 to thedesired position. Alternatively, the valve controller can be programmedto determine the correct position of valve 1002 based on temperaturedata passed to it by case controller 744, via rack PLC 720.

FIGS. 11–13 are block diagrams of aspects of a commercial refrigerationsystem according to FIGS. 7 and 8, including various systemconfigurations providing bus compatible modular case monitoring and/orcontrol. Briefly stated, FIG. 11 illustrates a system using buscompatible modular case controller (e.g., BCMCCs 744 and 802) to providecase monitoring and control functions for a plurality of refrigerationdisplay cases (not shown in FIG. 11). Similarly, FIG. 12 illustrates amodular case control system 1200 configured to provide case monitoringinformation for use by a system controller, such as, rack PLC 720, orthird party controller 746 (FIG. 7). Finally, FIG. 13 illustrates theuse of a modular case control system 1300 to provide branch control fora plurality of display cases comprising a refrigeration branch.

Referring now to FIG. 11, a first BCMCC 744 is constructed and arrangedto communicate with rack PLC 720 via control bus 741 (e.g., aLonWorks®/Echelon bus as shown in FIG. 7). A second BCMCC 802 isconstructed and arranged to communicate with rack PLC 720 via a wirelessRF interface (see also FIG. 8). It should be understood that FIG. 11 isprovided for exemplary purposes only; a given commercial refrigerationinstallation may include one or a plurality of BCMCCs, each havingeither a hard wired or wireless interface with a controller such as rackPLC 720 or third party controller 746.

Each BCMCC, in one construction, comprises a control unit (also referredto as a control module) and, possibly, one or more display units (alsoreferred to as display modules). The control unit is responsible fornetwork communications (e.g., control unit 744A communicates with rackPLC 720 via control bus 741). The control unit also includes a stepperdrive output for controlling an EEPR valve. The display unit receivessensor data from one or more associated sensors and controls the powerswitching of various fans, anti-sweat heaters, lights, and defrostheaters via an associated power switching module. As will be made clearby reference to FIGS. 12 and 13 below, one control unit can controlmultiple display units via a serial link. For example, in oneconstruction, one control unit is capable of interfacing with up toeight distinct display units. Thus, although FIG. 11 illustrates aconfiguration having one display unit per control unit, such aconfiguration is not required by the refrigeration system. Each controlunit and display unit, in one construction, includes a data processingcapability, as well as a data storage capability.

Using BCMCC 744 as an example, a display unit 744A receives temperatureinformation from one or more digital case sensors 1102. In oneconstruction, the digital case sensors 1102 are constructed such thatthey are individually addressed and provide case temperature data toBCMCC 744 in digital form over a single wire harness 1103. For example,a plurality of digital case sensors 1102 provide digital temperaturedata with respect to each display case controlled by BCMCC 744. It is tobe appreciated that one or more digital case sensors 1102 may be usedwith each case. Display unit 744B provides the digital temperature datato control unit 744A. Control unit 744A supplies the temperature data torack PLC 720 via control bus 741. Rack PLC 720 uses the temperaturedata, along with other system information, to determine appropriatedisplay case control activities. Further, based on system data,including this temperature data, rack PLC 720 determines an appropriateset point. The desired set point is transmitted to control unit 744A,which adjusts the EEPR valve 1104 accordingly. Rack PLC 720 alsodetermines when a particular case requires a defrost action, fan controlaction, or lighting action. Using case lighting as an example, rack PLC720 preferably determines when a particular case is to be illuminatedand provides an appropriate command to control unit 744A, which relaysthe command to display unit 744B. Display unit 744B asserts a signal online 1116 to cause a power switching module 1106 (also referred to as apower module) to activate the light(s) of the associated case(s).Similar control actions are taken for defrost cycling (via line 1112)and fan control (via line 1114). Anti-sweat control actions (e.g., foranti-sweat heaters associated with display fixtures having reach-indoors) are also accommodated by the display unit and power switchingmodule. It is noted, however, that many newer display fixtures do notrequire complicated anti-sweat controls.

Advantageously, each power module (e.g., power module 1106) can alsoserve as a local source of power for each BCMCC (including both thecontrol module and the display module). For example, local AC power (notshown) is supplied to BCMCC 744. Power module 1106 converts the local ACpower to DC power for use by BCMCC 744. Accordingly, the only wiringused to interface between a BCMCC with other devices in the controlsystem (e.g., rack PLC 720) is relatively low power signal wire, some ofwhich may be replaced by wireless interfaces, as explained herein.

When a BCMCC (e.g., BCMCC 744) is configured to control the powerswitching of display case activities (e.g., anti-sweat, defrost, fan, orlights), a separate power module (e.g., power module 1106) is, in oneconstruction, provided with each display unit, as shown in FIG. 11. If,however, a BCMCC is not used to control power switching of display caseactivities, only a single power module is used for each control unitassociated with the particular BCMCC. This aspect of the system isillustrated in greater detail with respect to FIGS. 12 and 13 below.

Although in the constructions illustrated in FIGS. 7, 8, and 11 eachBCMCC is ultimately controlled by a master controller (e.g., rack PLC720), one or more BCMCCs in a given refrigeration control system canoptionally be configured for peer-to-peer control/communication. Hence,multiple BCMCCs can share temperature data, time data, defrostscheduling data, and the like to improve system efficiency. For example,by sharing information regarding defrost timing, each BCMCC on a givencircuit can wait until all displays finish defrosting before starting arefrigeration cycle. By sharing information, such as current defroststatus information, each BCMCC is capable of initiating coordinateddefrost cycles to maintain minimum refrigeration load requirementsand/or ensure sufficient defrost gas (for gas defrost systems).

Advantageously, using the present modular case control system alsoimproves total system fault tolerance. In the event of a networkfailure, such as the loss of communications with rack PLC 720, eachBCMCC is, in one construction, configured to revert to an internalschedule and attempt to provide temperature control by determining theappropriate setting of its corresponding EEPR valve. Using BCMCC 744 ofFIG. 11 to illustrate this aspect, if communication with rack PLC 720 islost, BCMCC 744 attempts to maintain display case(s) temperature at themost recent set point by internally determining a desired setting forEEPR valve 1104. Similarly, display unit 744B continues to provide powerswitching control for display case activities on an internally derivedschedule.

An interface device 750 (e.g., a wireless device using an IR interface)supplies a capability to read and set case/fixture specific data. Asdescribed above with respect to FIG. 7, interface device 750 comprises aremote keypad for use with display unit 744B to access temperature dataand/or to input set point data. Thus, it is possible to input andmonitor set point data and other data associated with a display caseusing a BCMCC without the use of a master system controller, such asrack PLC 720. It should be understood, however, that when a mastercontroller is present, such controller would preferably override anyuser set points entered via interface device 750.

Optionally, each display unit (e.g., display unit 744B) can receive oneor more general purpose switch inputs. For example, a door open/closedinput 1150 can be supplied to display unit 744B when the display unit isused with a walk-in freezer. Display unit 744B could use the dooropen/closed input 1150 as an indication to turn off the fan(s) (via line1114 and power switching module 1106) whenever the door is open.Likewise, if door open/closed input 1150 may be used to set an alarmcondition, including an audible alarm, if a door is left open longerthan a threshold time (e.g., 5 minutes). Other possible switch inputsinclude a defrost temperature probe (not shown) that provides a discreteswitch signal at a preset temperature, indicating that a defrost cyclemay be terminated.

Referring still to FIG. 11, the operation of BCMCC 802 is substantiallysimilar to that of BCMCC 744. The primary difference between BCMCC 744and BCMCC 802 is that the latter illustrates the possibility of using awireless RF interface for communications between rack PLC 720 and BCMCC802.

FIG. 12 illustrates the use of a modular case control system (BCMCC1200) configured to provide fixture/case monitoring capabilities, butnot case control capabilities. In describing FIG. 12, other advantageousaspects of modular case monitoring and control using a BCMCC will becomeapparent. The BCMCC 1200 is arranged to receive sensor data from aplurality of digital case sensors (1205, 1207, and 1209) via a pluralityof display units (e.g., display units 1204, 1206, and 1208) over acommon digital data transmission channel/line 1212. Such sensor data, inone construction, comprises digital temperature data, as described abovewith regard to FIG. 11. A single power module 1210, provides power to asingle control unit 1202, as well as to all associated display units(1204, 1206, and 1208) and the sensors (1205, 1207, and 1209). Eachdisplay unit associated with BCMCC 1200 provides the sensor data to thecontrol unit 1202. Thus, only one control unit is needed to interfacewith a plurality of display units in the configuration illustrated inFIG. 11. The control unit 1202 supplies the sensor data received fromthe display units to rack PLC 720 or, alternatively, a third partycontroller (e.g., third party control 746 of FIG. 7). Rack PLC 720 canuse this information to control, among other things, a compressor (e.g.,using BCCSCM 48), a branch valve (e.g., using BCSBM 724), another systemvalve such as an EEPR valve (e.g., using BCVCM 726), or a condenser(e.g., using BCFCM 736), to achieve temperature control of the casesassociated with system 1200.

The configuration illustrated in FIG. 12 can also be used to illustrateanother example of how peer-to-peer communication and control are madepossible by the use of the distributed intelligence control system. Anassociated digital case sensor can determine the discharge airtemperature of each case being monitored by BCMCC 1200. In other words,the discharge air temperature of a first display case in a fixturelineup is monitored by a first digital case sensor (e.g., one of sensors1205) and provided to control unit 1202 by the first display unit 1204.Differences between control units and display units are discussed abovewith respect to FIG. 11. Similarly, the discharge air temperature of thesecond display case is monitored by a second digital case sensor (e.g.,one of sensors 1207) and provided to control unit 1202 by the seconddisplay unit 1206. This process is repeated for each display unit in thelineup. Control unit 1202 provides the discharge air temperature data torack PLC 720 over the control network. Rack PLC 720 uses thistemperature data to control a liquid line solenoid, via a branch controlmodule (e.g., BCSBM 724) as described above with respect to FIG. 9 toachieve temperature control for the case lineup associated with system1200.

Another of the many advantages of the distributed intelligence controlsystem can be appreciated by reference to the modular case monitoringsystem illustrated in FIG. 12. A single control unit 1202 can be used tomonitor a plurality of display units (e.g., display units 1204, 1206,and 1208), but each of the displays/fixtures associated with suchdisplay units need not necessarily be on the same refrigeration branch.For instance, if display units 1204 and 1206 are associated withfixtures on a low temperature branch and display unit 1208 is associatedwith a fixture on another branch, each branch can operate on separate(preferably non-overlapping) defrost schedules (which in the casemonitoring configuration illustrated in FIG. 12 can be controlled at therack by a branch control module or a valve control module). Because thesystem uses distributed intelligence, control unit 1202 receivesinformation from rack PLC 720 to allow each display to correctly reflectthe defrost status of the branch with which it is associated. Thus,using the example above, if the low temperature branch were in a defrostcycle, display units 1204 and 1206 would display a status messageindicating as such, while display unit 1208 would continue to displaypresent case temperature information. Accordingly, high degrees of casemonitoring and display granularity are maintained despite the fact thatonly one control unit is used.

FIG. 13 is a block diagram that illustrates a branch control systemusing a modular case control system 1300 for branch control functions.As illustrated in FIG. 13, the BCMCC 1300 includes a control unit 1302controlling a plurality of display units 1306, 1308, and 1310. A powermodule 1316 provides a local source of power for BCMCC 1300. The controlunit 1302 receives control commands from rack PLC 720 or, alternatively,a third party controller. Control unit 1302 also determines valveposition information from an EEPR valve 1304 and provides stepper motorcommands to position the EEPR valve 1304 in accordance with commandsfrom rack PLC 720 (or third party controller). In one construction,control unit 1302 determines the valve position of EEPR valve 1304 bymonitoring the number of steps applied and comparing that number to aknown starting reference. Periodically, the stepper motor may be“re-zeroed” to ensure proper control. When using a BCMCC to providebranch control, the EEPR valve is, in one construction, located with thedisplay case(s) rather than at the main rack with the rack PLC 720.Conversely, when branch control is achieved using a branch controlmodule (e.g., BCSBM 724 of FIG. 9) or a valve control module (e.g.,BCVCM 726 of FIG. 10), the EEPR valve is, in one construction, locatedat the main rack with rack PLC 720.

Referring still to FIG. 13, a commercial refrigeration branch caninclude one or more display cases associated with the display units1306, 1308, and 1310. A central controller, such as rack PLC 720,maintains branch control by monitoring various parameters associatedwith the refrigeration system. Such parameters can include, for example,temperature data, compressor data, suction data, and the like. In thebranch control system 1300 of FIG. 13, branch control is maintained bycontrolling the position of EEPR valve 1304. More particularly, rack PLC720 determines desired set points (e.g., discharge temperature) for thecase lineup associated with BCMCC 1300. Control unit 1302 receives theset point information over the control network and determines theappropriate position for EEPR valve 1304 to achieve the desired setpoint(s). In particular, control unit 1302 includes a stepper motordrive output connected to EEPR valve 1304 via line 1320. Hence, uponreceipt of the desired set point from rack PLC 720, control unit 1302determines the correct valve position and drives EEPR valve 1304 to thedesired position, thereby achieving the desired branch control function.

FIG. 13 can also be used to illustrate another example of howpeer-to-peer control/communication is available with the distributedintelligence refrigeration control system. If the discharge, suction, ormotor temperatures are high in every compressor and the valve openpositions according to the modular case controllers in the system (e.g.,BCMCC 1300) are not fully opened, the compressor controller (e.g.,BCCSCM of FIG. 7) sends a signal to the respective control units (e.g.,control unit 1302), via rack PLC 720, to open the valves (e.g., EEPRvalve 1304). If successful, such control action(s) reduce internalcompressor temperatures and improve efficiency and compressor lifeexpectancy. Similarly, if compressor temperatures are lower thanexpected (indicating, perhaps, a potential flood back condition thatcould damage or ruin a compressor), the compressor controller willsearch the system, via rack PLC 720, to determine which EEPR valves maybe open too far. Thereafter, the valves can be sequentially closed bysending commands to the respective control units (e.g., control unit1302), via rack PLC 720.

It should be understood, that the BCMCC 1300 illustrated in FIG. 13could be modified to provide single case control as well. In otherwords, BCMCC 1300 could be configured to provide complete branchcontrol, or single case control. It should further be understood thatone or more of the display units 1306, 1308, or 1310 can be configuredto provide power switching control in a manner described above withrespect to FIG. 11. In such a configuration, a power module would berequired for each display unit that provides power switching control(see FIG. 11).

As has been explained above, one of the advantages of the distributedintelligence control system is the ease with which such system isinstalled at a user site. The modular case control concept, exemplaryconfigurations of which are depicted in FIGS. 11–13, illustrates thispoint further. For example, each display unit (e.g., display units 1204,1206, 1208 of FIG. 12 or 1306, 1308, 1310 of FIG. 13) is, in someconstructions, automatically addressed by its associated control unit(e.g., control unit 1202 in FIG. 12 or control unit 1302 in FIG. 13). Inother words, upon installation of the system, the control unitautomatically determines how many display units are present, as well astheir address/location. More specifically, the control unitautomatically determines how many display units are attached. Thedisplay units are, in one construction, connected in serial fashion (aserial communication link from the control unit to the first displayunit, and then out of the first display unit and into the second displayunit, and so on).

In one construction, each display unit has the ability to disablecommunications with all other display units that are “downstream” of iton the serial communication channel/link. After power up, all of thedisplay units on a particular link are sent a command to disable theirindividual communications outputs. At this point, only the control unitand the first display unit are communicating; remaining display unitsare “cut off.” In this way, the control module (e.g., control unit 1202in FIG. 12) can now uniquely associate a first address with the firstdisplay unit (e.g., display unit 1204 in FIG. 12). After the firstdisplay unit is addressed, the control unit instructs this firstaddressed display unit to turn on its communications output, therebyre-connecting the second display unit (e.g., display unit 1206 in FIG.12) to the link. Now the control module can uniquely associate anaddress with the second display unit. This process is repeated until alldisplay units are addressed (e.g., until a communications failure occursindicating no more displays are present).

Further, each display unit, in one construction, polls each digital casesensor (e.g., sensor 1102 of FIG. 11) associated with that display unitto determine the location of the sensors and type, thereby associating aunique identification/address for each such sensor. The sensor locationand type information is forwarded to the control unit associated withthat display unit. In one construction, each digital case sensor to beused in a given case/fixture is configured in a wire harness prior toinstallation. Each sensor, in one construction, includes a memory (e.g.,an EEPROM) that is preprogrammed with a number that uniquely identifiesthe type of sensor (e.g., discharge air temperature, return airtemperature, inlet temperature, outlet temperature, product temperature,and so on), as well as the location in the case in which it will beinstalled (e.g., left side, center, right side). In this way, the systemis automatically configured upon installation, and end users and systeminstallers are not presented with the complexity ofprogramming/addressing the system at installation time. The digital casesensors are preferably located to provide temperature information thatfacilitate specific control functions. Such sensors include, forexample, discharge air temperature sensors, return air temperaturesensors, product temperature sensors, inlet and outlet refrigerationline temperature sensors, and defrost terminate sensors (e.g., sensorslocated on the evaporator or in the airstream).

FIG. 14 is a block diagram that helps to illustrate several of the manyadvantages of using a distributed intelligence refrigeration controlsystem. FIG. 14 is described by way of a specific example including afixture using modular case control (see FIGS. 11–13). This descriptionis for illustrative purposes only, and should not be construed aslimiting the scope of the invention.

A master controller 1402 (e.g., rack PLC 720) communicates with asubsystem controller 1406 (e.g., BCMCC 744) over a communication channel1404. For one construction, the only wiring between the mastercontroller 1402 and the subsystem controller 1406 is the communicationchannel 1404; no separate power wiring between them is required. Hence,master controller 1402 and subsystem controller 1406 receive powerlocally, thereby reducing the installation complexity of the system.Indeed, if communication channel 1404 is a wireless channel, no wiringis required between master controller 1402 and subsystem controller1406.

Each subsystem controller 1406 in the system is, in one configuration,constructed and arranged to operate one or more subsystem controlleddevices 1408 (e.g., an EEPR valve, a solenoid valve, a solid staterelay, a power switch, and the like) over one or more control lines1410. Thus, where multiple wiring runs may be necessary to providespecific control actions, only local wiring is required. In other words,long runs of control wiring are not required between the mastercontroller and the subsystem control device. For example, an EEPR valveassociated with a fixture line up is controlled locally; there is nodirect control wiring between the EEPR control valve and the mastercontroller.

Similarly, some subsystem controllers in the system are constructed andarranged to receive sensor input data, at a local level, from subsystemsensors 1412 over one or more sensor data busses 1414. For example, aplurality of subsystem sensors 1412 (e.g., digital case sensors 1307 ofFIG. 13) provide case temperature data with respect to a plurality ofcase monitoring locations. In this example, subsystem sensors 1412 areconstructed and arranged to communicate with subsystem controller 1406(e.g., display unit 1306) over a sensor data bus 1414 (e.g., a singletwisted pair communication bus). Subsystem controller 1406 transmits thesensor data to master controller 1402 over communication channel 1404(e.g., display unit 1306 transmits the data to control unit 1302, whichtransmits the data to rack PLC 720). Thus, master controller 1402receives remote sensor data without the need for installing complicatedand lengthy wiring between master controller 1402 and the remotelylocated subsystem sensors 1412.

An Appendix hereto includes a series of tables that provide additionalinformation regarding specific aspects of one construction of acommercial refrigeration control.

It is to be understood that the foregoing description, the accompanyingfigures, and the Appendix have been given only by way of illustrationand example, and that changes and modifications in the presentdisclosure, which will be readily apparent to all skilled in the art,are contemplated as within the scope of the invention, which is limitedonly by the scope of the appended claims. For example, as explainedherein, certain constructions are described with respect to a multiport(MPI) interface for use with serial, digital communications. Thoseskilled in the art having the benefit of the present disclosure shouldunderstand that other field bus configurations may be used, such asProfiBUS. ProfiBUS is a published standard, and MPI uses RS-485 at thehardware level but uses a proprietary data protocol from Siemens. BothMPI and ProfiBUS can be implemented in hard wired, wireless, orpartially wireless configurations. The use of the term hardwired isintended to include fiber optic systems. Furthermore, although multipleconstructions have been described, in part, in terms of bus systemsusing serial communication standards, the invention can be enjoyed usingserial and/or parallel bus structures.

It should also be understood that while aspects of the invention aredisclosed in terms of commercial refrigeration display cases, theinvention is not so limited. For example, the embodiments disclosed anddescribed herein may be used in other commercial refrigerationapplications such as, for example, cold storage rooms (e.g., meatlockers) and the like, as well as industrial, institutional, andtransportational refrigeration systems and the like. Accordingly, thespecific structural and functional details disclosed and describedherein are provided for representative purposes and represent thepreferred embodiments.

Further, for purposes of disclosing the numerous constructions, variousfeatures have been described by reference to specific terms, such asBCCSCM, BCSBM, BCVCM, and BCMCC. While these terms have been used toensure disclosure of the numerous constructions, they are the exclusiveintellectual property of the assignee of the present application.

In view of the above, it will be seen that the above constructionsprovide a wide variety of features and results. Manufacturing costs arereduced due to the use of fewer materials and components, as compared tonon-networked refrigeration systems. Similarly, fabrication andinstallation is simplified due to the elimination of high voltagewiring, typically required by prior art systems. The use of modularityallows for standardized manufacturing techniques, while stillaccommodating customer requirements, such as interfacing with thirdparty control and monitoring devices over standardized communicationinterfaces. Such improvements in manufacturing, fabrication, andinstallation also translate into improved system serviceability. Theincreased granularity of the system resulting from using a distributedcontrol architecture increases the fault tolerance of the system.Implementing the system using optional wireless communication links(e.g., via RF links) where relatively large distances exist betweennetworked components eliminates the cost for installing hardwired links.Such optional wireless links, by their nature, provide improved damageresistance from external problems such as lightening strikes, highvoltage arcing, or high current transmission in adjoining equipment andwiring.

Appendix

Table 5 provides an overview of an exemplary preferred hardware andnetwork connection set for several components of a refrigeration systemsuitable for use according to the invention illustrated and discussionherein.

Device Target Platform Network Connections Rack PLC Siemens S7-300 AS-i;LonWorks ®/ CPU314 Echelon; TCP/IP; MPI Condenser PLC Siemens S7-300MPI; AS-i CPU314 Remote HMI Siemens TP170A MPI Local HMI Siemens OP3 MPIBCCSCM Atmel AT90S2813 AS-i BCSBM Siemens 4 Out AS-i AS-i Module BCVCMAtmel AT9052813 AS-i; LonWorks ®/ Echelon BCFCM AMI S4 AS-i ASIC AS-iBCMCC Echelon Neuron LonWorks ®/ Echelon Local Workstation Windows NTTCP/IP

Table 6 provides an overview of an exemplary set of preferredinput/output (I/O) devices controlled by rack PLC 720 according to thepresent invention.

I/O Specifications Controlled Devices Max. Network I/O DeviceCompressors 16 AS-i BCCSCM System Valves 256 LonWorks ®/ BCVCM (MotorActuated) Echelon System Valves 64 AS-i BCSBM (Solenoid Actuated) CaseLighting Circuits 32 AS-i AS-i 4 Out Condenser Fans 16 MPI Condenser PLCSatellite Compressor 2 AS-i BCCSCM Suction Groups 4 N/A N/A

Table 7 identifies a preferred set of analog inputs, with exemplaryranges, for use by rack PLC 720 to provide refrigeration control inaccordance with the invention.

Analog Inputs Input Range Max. Network I/O Device Ambient −40°–120° 1MPI Condenser PLC Temperature Liquid Line −40°–120° 1 Local S7 AnalogI/O Temperature Heat Reclaim   0–500 PSI 2 Local S7 Analog I/O PressureReceiver Level  0%–100% 1 Local S7 Analog I/O System Case −40°–120° 256LonWorks/ Echelon BCMCC Temperature Suction Pressure   0–200 PSI 32 AS-iBCCSCM Suction −40°–120° 32 AS-i BCCSCM Temperature Discharge   0–500PSI 32 AS-i BCCSCM Pressure Discharge  0°–275° AS-i BCCSCM TemperatureCompressor   2–100 A 1 per AS-i BCCSCM Motor Current compressor

Table 8 identifies a preferred set of analog inputs, with exemplaryranges, for use by rack PLC 720 to provide refrigeration control inaccordance with the invention.

Digital Inputs Input Range Max. Network I/O Device System DefrostTrue/False 32 AS-i BCSBM Termination Bi-Metal Thermostat Heat ReclaimStatus True/False 1 Local S7 Digital I/O Compressor Phase True/False 32AS-i BCCSCM Reversal Compressor Phase True/False 32 AS-i BCCSCM LossCompressor Internal True/False 32 AS-i BCCSCM Protect Fail CompressorRun  0–99999 32 AS-i BCCSCM Time Compressor Oil True/False 32 AS-iBCCSCM Fail EEPR Valve 0%–100% 256 LonWorks/ BCVCM Position Echelon

Table 9 identifies a preferred set of capacity-related control functionsassociated with rack PLC 720.

Capacity Control Compressor Cycling Methods Control Parameter First OnFirst Off Suction Pressure Suction Pressure Reset Programmed Sequence(Uneven Comp. capacity) Real Time Sequence Reconstruction Other CapacityControl PWM Control Pressure/Temperature Unloader supportPressure/Temperature Variable Speed Drive Pressure/Temperature controlSatellite Control Pressure/Temperature

Table 10 identifies a preferred set of system branch control functionsassociated with rack PLC 720.

System Branch Control Defrost Case Temperature Control Scheduling/ TODClock Liquid Line EEPR Suction Initiation Solenoid Ctrl Ctrl TerminationTime Temperature/Bimetal Thermostat Drip Cycle (User selectableduration) Defrost Types Case Lighting Electric Heater Ctrl TOD ControlBranch Liquid Line Ctrl Gas Liquid Line Ctrl Off Time Branch Liquid LineCtrl EEPR = Electronic Evaporator Pressure Regulator

Table 11 identifies a preferred set of refrigeration system valve andcondenser control functions associated with rack PLC 720.

Control Parameter Valve Control Flooding Valve Control Motor DrivenReceiver Level Discharge Pressure Solenoid Actuated Receiver LevelDischarge Pressure Heat Reclaim Lockout control Solenoid ActuatedDischarge Pressure H.R. Coil Pressure Main Liquid Valve Motor DrivenDischarge Pressure Receiver Pressure Solenoid ActuatedPressure/Temperature Receiver Pressure Regulator Motor Driven AutoDischarge Pressure Receiver Pressure Surge Valve Motor Driven SplitCondenser Valve Solenoid Actuated/ Discharge Pressure/ Condenser FanHistory Motor Driven Condenser Control Function Fan Cycling DischargePressure/Liquid Refrigerant Temp. Condenser Split DischargePressure/Outdoor Amibient Temp.

Tables 12 and 13 identify a preferred set of alarm conditions for therefrigeration system controlled by rack PLC 720. Table VIIIA identifiesconditions having separate alarms associated with hi conditions and lowconditions. Table VIIIB identifies conditions having a single systemalarm. Both Table VIIIA and VIIIB identify, whether the condition islogged, whether the condition is displayed in real time, a preferredminimum update interval (MUI), and the accuracy of the measuredcondition.

Monitoring and Alarm Label Source Hi Alarm Lo Alarm Data Log RT Disp MUIAcc. Suction BCCSCM Yes Yes Yes Yes .5 sec .1 PSI Pressure SuctionBCCSCM Yes Yes Yes Yes .5 sec .5° Temp Discharge BCCSCM Yes Yes Yes Yes.5 sec 1 PSI Pressure Discharge BCCSCM Yes Yes Yes Yes .5 sec  1° TempCase BCMCC/ Yes Yes Yes Yes .5 sec .5° Temp Local I/O Ambient CondenserN/A N/A Yes Yes .5 sec .5° Temp PLC Liquid Local I/O N/A N/A Yes Yes .5sec  1° Line Temp Receiver Local I/O N/A N/A Yes Yes .5 sec 1 PSI Pres.Receiver Local I/O Yes Yes Yes Yes .5 sec 1% Level Liquid Local I/O N/AYes Yes .5 sec 1 PSI Pres. Motor BCCSCM Yes Yes Yes Yes .5 sec ±2 ACurrent

Monitoring and Alarm (cont.) Label Source System Alarm Data Log RT DispMUI Acc. Def/Ref Internal N/A Yes Yes N/A N/A Status Clock Oil FailBCCSCM Yes Yes N/A .5 sec N/A Phase Loss BCCSCM Yes Yes N/A .5 sec N/APhase BCCSCM Yes No N/A .5 sec N/A Reversal Comp BCCSCM Yes Yes N/A .5sec N/A Internal Heat Local I/O N/A N/A Yes .5 sec N/A Reclaim I.O. HeatHVAC N/A Yes Yes .5 sec N/A Reclaim Input Stat. Auto Surge BCVCM N/A YesYes .5 sec .1% Valve Stat* Main Liq. BCVCM N/A Yes Yes .5 sec Line Pres.Differential % Pos % Pos Valve Split Cond Internal N/A Yes Yes .5 secN/A Stat Flooding BCVCM N/A Yes Yes .5 sec .1% Valve Stat % Pos % PosReceiver BCVCM N/A Yes Yes .5 sec .1% Pres Reg. All Comp Internal YesN/A N/A N/A N/A Off Cond Fan Internal N/A Yes Yes .5 sec N/A Status

Table 14 illustrates aspects of a preferred embodiment of a local HMIdevice 754, suitable for use in the commercial refrigeration systemsdepicted in FIGS. 7 and 8.

Hardware Detail Siemens TP 170A Siemens Part No. TP 170A6AV6545-0BA15-2AX0 I/O Specifications Controlled Devices Range Max.Network I/O Device Alarm Output N/A 1 N/A N.O. Relay Functions SystemConfiguration Status Display Site Layout Refrigeration Status BranchSystem Configuration Branch System Status Refrigeration ConfigurationAlarm Status Alarm Configuration Condenser Status Data LoggingConfiguration Site Status Diagnostic Display Maintenance DisplayHistorical Graphing I/O Forcing Real Time Graphing Run Time MeterMaintenance Alarm History Set Clocks User Logs Clear History

Table 15 illustrates aspects of a preferred embodiment of a remote HMIdevice 752, suitable for use in the commercial refrigeration systemsdepicted in FIGS. 7 and 8.

Hardware Detail Siemens OP3 Siemens Part No. TP 170A 6AV6545-0BA15-2AX0I/O Specifications Controlled Devices Range Max. Network I/O DeviceAlarm Output N/A 0 N/A N.O. Relay Functions System Configuration StatusDisplay Local Branch System Configuration Refrigeration Status LocalRefrigeration Configuration Branch System Status Rack AlarmConfiguration Alarm Status Condenser Status Diagnostic DisplayMaintenance Display Alarm History I/O Forcing Run Time Meter MaintenanceSet Clock Clear History

Various features and advantages of the invention are set forth in thefollowing claims.

1. A method of operating a compressor control module associated with acompressor of a refrigeration system, the compressor control modulebeing adapted to communicate with a system controller operable tocontrol the refrigeration system, the method comprising: at thecompressor control module, monitoring a parameter of the compressorincluding obtaining a value for the parameter; comparing the value witha parameter limit; generating an alarm after the value traverses theparameter limit; communicating the alarm to the system controller;replacing the compressor control mofule after generating the alarm; andreconfiguring the system including the replaced compressor controlmodule.
 2. A method as set forth in claim 1 wherein the replacing actincludes replacing the compressor connected to the compressor controlmodule.
 3. A method as set forth in claim 1 wherein the refrigerationsystem is a commercial refrigeration system.
 4. A method as set forth inclaim 1 wherein the parameter is selected from the group consisting ofdischarge pressure high, discharge temperature high, motor current high,oil pressure, and motor temperature.
 5. A method as set forth in claim 1wherein the communicating act includes communicating information relatedto the alarm to the system controller.
 6. A method as set forth in claim1 wherein the communicating act includes communicating informationrelated to the alarm to the system controller, the information includingan identification of the parameter and the value of the parameter.
 7. Amethod as set forth in claim 1 wherein the communicating act includescommunicating information related to the alarm to the system controller,the information including an identification of the parameter, the valueof the parameter, and a time and date of the alarm.
 8. A method as setforth in claim 1 wherein the compressor control module is supported bythe compressor.
 9. A methof of operating a compressor control modulecoupled to a compressor of a refrigeration system, the compressorcontrol module including a processor, a memory, and a sensor coupled tothe compressor, the refrigeration system comprising a condenser, avalve, and a refrigeration branch having an evaporator coil, all ofwhich being in fluid communication with the compressor, therefrigeration system further having a system controller operable tocontrol one or more aspects of the refrigeration system, the methodcomprising: at the compressor control module, occasionally receivinginstructions from the system controller for operating the compressor;monitoring a parameter of the compressor including obtaining a value forthe parameter; comparing the value with a parameter limit; generating analarm after the value traverses the parameter limeit; communicating thealarm and information relating to the alarm to the system controller;and deactivating the compressor after generating the alarm and prior toreceiving further instructions from the system controller.
 10. A methodas set forth in claim 9 and further comprising: replacing the compressorcontrol module after generating the alarm; and reconfiguring the systemincluding the replaced compressor control module.
 11. A method as setforth in claim 10 wherein the replacing act includes replacing thecompressor connected to the compressor control module.
 12. A method asset forth in claim 9 wherein the information includes an identificationof the parameter.
 13. A method as set forth in claim 9 wherein theinformation includes an identification of the parameter and the valuefor the parameter.
 14. A method of operating a compressor control moduleassociated with a compressor of a refrigeration system, the compressorcontrol module being adapted to communicate with a system controlleroperable to control the refrigeration system, the method comprising: atthe compressor control module, monitoring a parameter of the compressorincluding obtaining a value for the parameter; comparing the value witha parameter limit; generating an alarm after the value traverses theparameter limit; and communicating the alarm to the system controller,including communicating information related to the alarm to the systemcontroller, the information including an identification of theparameter.
 15. A method as set forth in claim 14, wherein theinformation further includes the value of the parameter.
 16. A method asset forth in claim 15, wherein the information further includes a timeand date of the alarm.
 17. A method as set forth in claim 14 wherein thecompressor control module is supported by the compressor.